For months after it happened, through sweaty South Carolina days and cooler starlit nights, even when the air eventually grew so chilly that she could see her breath, Katie Lesslie sat curled up in the cushioned porch swing of her white house in the woods, staring past her backyard and into the distance.

Images flashed through her head: her two children, Adah, 9, and Noah, 5, playing over there to her left, climbing on rocks and running wild on ground made soft by fallen pine needles.

Her father-in-law, clad in his doctor’s scrubs, playing “Highland Cathedral” on his bagpipes outside his house.

Her mother-in-law, whose motto was “if it’s worth doing, it’s worth overdoing,” in her kitchen cooking family favorites like B’s favorite mud pie.

As Katie sat and thought, her husband, Jeff, brought her food. And fuzzy blankets. And boxes of tissues, to wipe away their never-ending tears as they searched for an answer to a question that had none.

Their life in Rock Hill, S.C., had been idyllic, rooted in Christian faith and service, and centered around a 50-acre family compound, a place the Lesslie clan called The Land.

Jeff’s parents, Dr. Robert and Barbara Lesslie, bought the property in 2002, hoping that their four children would build houses of their own there.

The plot had been just brambles and loblolly pine trees planted in rows for future harvest. With long, slender trunks, the pines looked like an army of matchstick soldiers so tall that they touched the sky.

Dr. Lesslie had a wondrous vision for his real estate. Three ponds stocked with bass and bream. A stage and a field for music festivals. A little barn for mini-donkeys, mini-horses and goats. An 18-hole Frisbee golf course.

The anchor of it all would be a big brown house for him and his wife, and it would become known as the big house.

And then someone they had never met, someone they had never even heard of, showed up and shattered that bliss, leaving behind a level of pain that could break any family’s bond.

‘Where are my kids?’

Katie, a preschool teacher, was home for spring break on April 7, 2021, her 36th birthday. Recovering from a Covid shot, she was napping while her children were at the big house with their grandparents. Jeff was in town, running his hospice and palliative care business.

Around 4:45 p.m., the hysterical barking of the family labradoodle, Gibson, jolted Katie awake. She then heard police sirens growing louder.

She raced to the big house. A landscaper who had been mowing the lawn stopped her short. He was on a call to 911. Police cars were pulling in.

“Where are my kids?” Katie asked him.

He just said, “I’m sorry. I’m so sorry.”

Two heating and air conditioning technicians, both fathers of three, had been shot in the driveway. One, James Lewis, was on the ground, motionless. The other, Robert Shook, had been shot multiple times, but somehow managed to call his boss to tell him what happened. He would later die from his wounds.

A police officer stopped Katie from getting any closer to her in-laws’ house. The shooter had not been apprehended. She called Jeff and his sister Amy Kulbok, who also lived on the property.

For what seemed like hours, but was probably just 10 minutes, Katie waited at a cedar tree maybe 100 feet from the front door of the big house. She watched as troops of law enforcement officers swarmed the area.

SWAT teams, state and local police and teams of police dogs. The thump of helicopter blades droned from above, drowning out the chirping cicadas. Again and again, she shouted, “Where’s the ambulance?”

As a police officer watched over her, a voice came over his walkie-talkie, too quickly for him to silence it.

“There were four people in the house,” it said. “They’re all gone.”

Katie turned numb.

“I heard screaming and I couldn’t figure out where it was coming from,” she told me recently, in the family’s first interview since the shooting. “And then I realized it was coming from me.”

Katie joined Jeff and Amy on the adjacent county road. Jeff asked his sister, “Is it true?” She nodded.

He threw a water bottle at a tree. And then he grabbed another tree with both hands and dug his nails into its thick bark. He thought of the shooter and shouted, “Lord, forgive him!”

Amy, a trauma therapist with a master’s degree in Christian counseling, had been standing behind Jeff, with her hand on his shoulder.

“That’s how we’re going to do this,” she said. “That’s how we’re going to proceed.”

The crime scene

Living in Rock Hill, known as Football City, U.S.A., the Lesslies were surrounded by the game, and many of them were fans of it.

For years, Dr. Lesslie had season tickets to the University of South Carolina and the Carolina Panthers. Jeff helped Adah memorize the Panthers’ theme song.

The town of about 75,000 claims to have churned out more N.F.L. players per capita than any other town, locals say — so many that the Lesslies were not aware of all of them. They didn’t know that a former N.F.L. player, Phillip Adams, was living with his parents a quarter-mile down the street.

Adams, a standout high school cornerback who went on to play at South Carolina State, was chosen in the seventh round of the N.F.L. draft and bounced around the league — six teams in all — from 2010 to 2015, before returning to Rock Hill.

After football, he lost his way. He struggled to find a new career. Responsibilities weighed on him. He helped care for his mother, Phyllis Paden-Adams, a teacher who became a paraplegic after a car accident. He also had a child to support.

Friends and family said Adams struggled with memory loss and mental health issues and had shown increasingly aggressive and erratic behavior.

And then on one warm spring day, Adams, 32, left his parents’ house and hopped onto his blue four-wheeler, headed toward The Land. He was carrying two submachine guns.

He jumped over a fence, emerged from the woods, walked to the driveway of the big house and opened fire on the two HVAC workers.

As far as the Lesslie siblings — Jeff, Amy, Lori and Robbie — can surmise based on their mother’s wedding rings sitting near the kitchen sink, she had been preparing a meal there, with Adah and Noah watching television behind her, when she looked through the window and saw Adams shoot the workers.

She ran to lock the front door and rushed the children to the exercise room, where Dr. Lesslie was on his elliptical machine. Adams shot through a window, unlocked the door and followed them.

He shot Barbara Lesslie five times in the back as she tried to protect her grandchildren. He shot Dr. Lesslie seven times. The police later recovered two dozen spent bullet shells and projectiles from the property. Law enforcement officers who saw the crime scene were offered counseling.

Adams dropped his cellphone on his way out, and the police found him at his parents’ house. Hours later, after a standoff, he shot himself in the head.

He had left no note, no explanation. He was not one of Dr. Lesslie’s patients. Investigators found no connection.

“I think the football messed him up,” Alonzo Adams, his father, told a local television station, raising the question of whether the head injuries he sustained during his career played a role in his decision to kill six strangers.

What followed has become something of a rite of passage for the N.F.L.’s deceased. A medical examiner extracted Adams’s brain from his skull and shipped it on ice to a lab where neuropathologists would slice it, stain it, scan it and look for clues that might explain the former player’s behavior.

Their goal was to find out if he had chronic traumatic encephalopathy, or C.T.E., the degenerative brain disease linked to repeated blows to the head in contact sports like football. Its symptoms include mood disorders, memory problems and impulsive behavior, and it has been found in hundreds of former football players.

‘You and Me’

Each day felt endless as the Lesslie family tried to move forward against the swells of grief.

News helicopters circled above. Reporters called and visited, hoping to conduct interviews. Speculation about motives spread on social media.

The script was familiar for a mass shooting. Scrutinize the killer. Examine the victims’ past. Await the reaction from the victims’ families, be it uncontrollable sorrow or rage, or calls for gun control or retribution.

The Lesslies chose an uncommon path. Their initial public statement said that as followers of Jesus Christ, they were “enveloped by peace that surpasses all understanding.”

They wrote: “To that end, our hearts are bent toward forgiveness and peace. Toward love and connectedness. Toward celebration and unity.”

They wanted the public to know that they were not angry with Adams. There was no room for hate in their already bursting hearts.

Katie later described their ability to forgive, and forgive so quickly, as an inexplicable gift from God.

Amy said, “I see the preparations of God’s handiwork for years and years in advance, kind of leading to where we are.”

Growing up in Rock Hill, the Lesslies attended the First Associate Reformed Presbyterian Church each Sunday, and the four siblings said they felt loved, free and sometimes feral — as teens they hosted rowdy house parties with bands when their parents were away — and that it forged an inseparable bond.

Their Scottish clan motto is Grip Fast, and they were so close that they got similar tattoos: a figure that represented their mother, holding out her arms. Each of her children, as stick figures, were hanging from her.

Dr. Lesslie, who was 70, was a respected doctor: He worked in and directed emergency rooms for 25 years, started an urgent care center and opened a hospice service. He also was the author of a popular series of Christian-themed books that were often sold in airports, including one called “Angels in the E.R.,” about inspiring stories he had witnessed on the job.

Barbara Lesslie, 69, was a beloved staple at a place called Camp Joy, a Christian camp in the Blue Ridge Mountains of North Carolina. It serves adults and older teenagers with intellectual and developmental disabilities like autism or Down syndrome, and all the Lesslies, young and old, helped out there every summer.

Dr. Lesslie was known there as Dr. Rob, the camp doctor who would start the day by playing “Amazing Grace” on his bagpipes. Mrs. Lesslie was Ms. B, a Bible teacher, and her animated lessons were fueled by her time in community theater. She had long joked that she wanted her ashes scattered onto a Broadway stage.

Jeff, now the executive director of the nonprofit that runs Camp Joy, met Katie there more than 24 years ago when they were counselors.

“Something changed in me when I first went,” Jeff said. “And then the Lord put his hooks in all of us.”

After the murders, the Lesslies saw signs from God that comforted them. Lori, whose married name is Lori Alexander, found a note in their mother’s Bible, written in their mother’s cursive. The words on it were, “How to live in troublesome times,” and “God controls our circumstances! God will meet our needs! God is with us!” and she mentioned Romans chapter 8, which promises deliverance despite current suffering.

On their father’s night stand, the children found a book called “Suffering” by Paul David Tripp. One passage Dr. Lesslie had marked with a red star recommended that people avoid bitterness because “it erodes your motivation to do the good and constructive things that every sufferer needs to do so as not to lose his way.”

One day, Jeff walked the grounds, winding his way through the orchards of apples, figs and pears, crying while pondering the idea that his parents were his past and his children were his future. Thinking about Adah and Noah, he asked God, “Show me, I just need to know they are OK.”

He went into his silent house and climbed onto Noah’s bed, burying his face in the little bear security blanket to soak in the scent of his son. Then he got on Adah’s bed and hugged her green blanket.

Atop her stack of “Harry Potter” books, he found an empty notebook with a piece of paper tucked into it. On it was a song Adah had written called “You and Me.”

You and Me… we can love one another. Even through the hardest times. Even through the darkest days, we can love one another. Even in the deepest fog, we will find one another and love each other. When people see us they will see Jesus Christ in You and Me.

It ended with “Ooh” written in big, rounded letters 16 times, and Jeff could hear his daughter singing it.

The villain

Dr. Ann McKee, a neuropathologist at Boston University and the world’s leading expert in C.T.E., has studied thousands of brains for the disease. She runs a C.T.E. brain bank at the V.A. Boston Healthcare System that is filled with them, most from former athletes who competed in contact sports.

Families hope she can find an explanation for their loved one’s behavior. Why had that person turned into someone they did not recognize? Why had he become so paranoid and depressed? Why did he kill himself? And why, in a growing number of cases, did he decide to kill others?

To find answers, Dr. McKee and her team examine the brains with microscopes, magnifying glasses and scanners, while family members and other interested parties — like the Lesslies — anxiously wait.

It is an excruciating wait filled with fears and tears. A wait that Katie Lesslie mostly spent on her porch swing.

Eight months after the shooting, Dr. McKee delivered her report at a news conference held by the county coroner, and the Lesslie family gathered in Amy’s living room to watch it.

Dr. McKee announced that Adams had stage 2 C.T.E.

She said that Adams’s 20 years in football caused the disease, explaining that stage 2 was associated with aggression, impulsivity, explosiveness, depression, paranoia, anxiety, poor executive function and memory loss.

Dr. McKee called Adams’s frontal lobe damage unusually severe, similar to that of another former N.F.L. player, Aaron Hernandez of the New England Patriots, and that it might have contributed to his homicidal behavior. She pointed out, however, that there are usually multiple reasons a person becomes homicidal, and that physical, psychiatric and social factors can come into play.

In 2015, Hernandez was convicted of shooting and killing a man. He was 27 when he killed himself in prison.

“C.T.E. is the villain of this story,” Amy decided. “This has to be it. This is the only thing that makes sense.”

Two versions of grief

The Lesslie family met face-to-face with Adams’s parents in August 2023 after many failed attempts to connect.

Rev. Dr. Carlton Brown, the Adamses former pastor and a chaplain at the sheriff’s office during the shooting, had brokered the meeting, hoping it would help both parties heal. Three pastors from three churches attended. All three said they were amazed by what they witnessed.

They gathered in a building across from the New Mt. Olivet A.M.E. Zion Church in Rock Hill, the Adams family’s parish, and sat at a table in a large room with empty beige walls and beige vinyl floors. Jeff Lesslie broke the tension with a story.

He told Adams’s parents that he had the clearest vision in his head of Adams, Adah and Noah. They are in heaven, and Adams is pushing the kids on a swing. He paused and said, “I am so sorry for your loss.” He told them that he was relieved to have forgiven Adams while he was still alive.

Struggling to talk, Ms. Paden-Adams apologized and asked for forgiveness. But the Lesslies stopped her, saying it was not their fault. C.T.E. had turned Adams into someone else, they said. The families hugged and cried and said they had been praying for each other.

“We were living with a whole different set of grief, and theirs is a grief I can’t understand,” Katie said later. “But I do know what it’s like to be a mama who lost her son. That is our level playing field.”

Rev. Angela Boyd, the pastor of the New Mt. Olivet Church, said one of her lasting takeaways was that the N.F.L. should take better care of its players.

The N.F.L.

The whole Lesslie family started reading about C.T.E. when Adams’s brain was sent to be studied. After years of research, Katie and Jeff wrote to Dr. McKee in the fall of 2024, asking to meet her. They said they wanted to learn about her C.T.E. studies on football players.

Katie went to the meeting in Boston with a list of more than a dozen questions, including: “What steps can be taken to care for players that are showing signs of C.T.E.? What steps can be taken to prevent C.T.E. in the first place?”

They now joke that they earned a Ph.D. in C.T.E. in the two days they spent with Dr. McKee and her team. They donned lab gear and watched her dissect and examine a brain. They listened to presentations about C.T.E. research and the brain bank program, and examined slides and images of Adams’s brain.

The Lesslies left believing that football officials at all levels, especially those in the N.F.L. because of the league’s extraordinary influence on the sport, had failed to protect Adams. If not for C.T.E., they said, the murders would not have happened.

“The question is, could it have been prevented, yes or no?” Jeff said of the shooting. “If yes, then you have to do something to fix it. And, based on everything we’ve seen and heard, we believe it was yes.”

Adams’s parents, through their lawyer who is handling a wrongful death lawsuit against South Carolina State and the N.F.L., declined to comment.

The N.F.L. declined to comment on the Lesslies’ criticisms of the league. Instead, in an emailed statement, a spokesman said the league supports “the long-term health and well-being of every player, both on and off the field,” including retirees with neurocognitive disorders.

Jeff misses football. But he said he can’t watch again until the N.F.L. and football’s youth, high school and college organizers do more to make the sport safer.

In particular, he and Katie said, families need to know more about C.T.E. so they can make an informed decision about their children’s participation.

In Rock Hill, tackle football starts at age 7.

“Your son, who’s 7 now, looks so adorable and real cute in that jersey and huge pants,” Katie said. “But you know what could happen? That 7-year-old could turn 32 and walk a quarter of a mile down the road and kill six people. That’s the danger of football.”

The Land

After the shooting, the Lesslies were drawn to the big house.

Lori, an assistant high school principal who lives in Georgia, had the bullet holes repaired and slept in the bedrooms, determined to preserve it as a happy place. Jeff played his guitar there, singing tunes he used to sing to Adah and Noah at bedtime.

Katie told no one that she was sneaking off in the mornings, before sunrise, to work out on the rowing machine in the big house’s exercise room. Its stained and damaged flooring had been replaced.

She would row and row, focusing on Adah, her insatiable reader who had tackled “Little Women” at 7, and Noah, her boisterous butterball of a boy who was always trying to make people laugh with physical comedy.

At times, Jeff and Katie wanted a break from the memories. Their house, especially its two vacant bedrooms, sometimes made Katie physically ill. Jeff had flashbacks whenever he heard bullfrogs croaking. That sound had been so loud the days after the shooting as he walked the well-worn path from his house to Amy’s.

But the agony followed them away from home, too, where people often ask them, “Do you have children?” Sometimes they say yes, they have two, and they are waiting for them in heaven. Other times, when they don’t want to make someone feel uncomfortable, they do something that feels so wrong. They answer, “No.”

Knowing they could not escape their sorrow, they all chose not to move away from the property Dr. Lesslie had officially christened with the name Siochain. In Gaelic, it means peace.

One of Jeff’s best friends bought the big house, and Jeff still has the key. He goes there when his friend is out of town to house sit or walk the dog. When inside, he slides his hands along the walls. He lies on the floors.

The Land has a way of absorbing grief, the family said.

Yet the emptiness lingers.

Audio produced by Jack D’Isidoro.