Charlie Kirk's reach and influence over the conservative community was a crucial factor not only in the Republican Party's message, but also to President Donald Trump's political rise.
Trump took to his social media site on Wednesday shortly after the reports about Kirk getting shot at an event in Utah, asking Americans to pray for the 31-year-old social media activist with whom he and his family had a close personal relationship as well as a political one.
He later posted on his social media site the word that Kirk had died.
"No one understood or had the Heart of the Youth in the United States of America better than Charlie. He was loved and admired by ALL, especially me, and now, he is no longer with us. Melania and my Sympathies go out to his beautiful wife Erika, and family. Charlie, we love you!" Trump posted.
"I love you brother. You gave so many people the courage to speak up and we will not ever be silenced," Donald Trump Jr. posted about the Trump family ally.
An Illinois native, Kirk had two children, a 3-year-old girl and a 1-year-old boy.
"It’s horrific. It’s one of the most horrible things I’ve ever seen," Trump told ABC News Chief Washington Correspondent Jonathan Karl before he announced Kirk's death.
The president ordered all U.S. flags to be flown at half-staff until Sunday evening.
The shooting had rattled most everyone inside the White House. Shock, anger, sadness, disbelief were words used by multiple senior sources inside the West Wing, ABC News' Katherine Faulders said.
Though Kirk was not a White House staffer, he was a constant and visible presence at the White House, she reported. Kirk, who was known as the "Trump whisperer," was deeply involved in vetting top positions for the administration since the election and was in constant communication with top advisers and the president himself.
Trump had attended many events hosted by Kirk's conservative advocacy group, "Turning Point USA," which helped to promote the president, especially with high school and college-age voters. The group and Kirk had a huge following with conservatives, particularly men, and he was able to parlay that popularity into support for Trump's campaign.
He was considered a huge star on the far right by many conservative pundits and seen as leading the next generation of Trump's MAGA movement, and while very close to the administration, had not been afraid to push back at times, ABC News Chief White House Correspondent Mary Bruce reported.
Earlier, during the 2016 Republican National Convention, Kirk spoke to an enthusiastic crowd as one of the event's youngest speakers. During the campaign, he worked with Donald Trump Jr., Eric Trump and Lara Trump on the trail, and assisted them with their social media outreach.
Some considered Kirk to be an extended member of the Trump family.
Kirk began his political punditry while in college, writing essays for conservative publications like Breitbart News and The Daily Caller. He co-founded Turning Point in 2012 at the age of 18 and the organization gained popularity among conservative circles, particularly younger members.
The organization boasts on its website that it currently has "a presence on over 3,500 high school and college campuses nationwide, over 250,000 student members, and over 450 full- and part-time staff all across the country."
Trump and his allies praised Kirk, who was 22 at the time, for his ability to attract younger voters to the conservative cause, dubbing him the "conservative boy wonder."
"Amazing job. He's done something that is just incredible for somebody really of his age. You need tremendous talent to do what he's done. Building one of the most powerful youth organizations ever created--Turning Point USA. And I want to thank you, Charlie. Incredible job," Trump said in 2019.
After Trump was elected to office, Kirk used his influence to speak out against the president's opponents and attack liberal policies. Kirk spread falsehoods about voter fraud during the 2020 election and misinformation about the COVID-19 vaccine.
In April 2020, Kirk called on members of Turning Point USA's Students for Trump to launch a "peaceful rebellion against governors," over pandemic lockdowns.
Kirk, who was the opening speaker at the 2020 RNC, said on Jan. 5, 2021, that Turning Point Action and Students for Trump, which he founded, was sending 80 "buses of patriots to D.C. to fight for this president." Kirk would later plead the Fifth Amendment when he testified in 2022 before the U.S. House Select Committee on the Jan. 6 attack on the U.S. Capitol by a pro-Trump mob.
He remained close with Trump after he left office in 2021 and continued to push his ideas during tours to college campuses, his podcast, essays and other media appearances.
During the 2024 election, Turning Point helped Trump with get-out-the-vote operations in battleground states targeting smaller groups of engaged voters. He also tried to influence the outcome of the vote by impelling Nebraska to implement a winner-take-all electoral system and encouraging Republican leaders to make that change.
Trump showed his appreciation for Kirk and his efforts right after the election by visiting a Turning Point event in Arizona.
"I want to express my tremendous gratitude to Charlie Kirk. He's really an amazing guy, amazing guy and his whole staff for their relentless efforts to achieve this very historic victory … It's not my victory, it's your victory. It's a great honor," Trump said.
Kirk became a frequent presence at the White House during Trump's second term, in some cases in the Oval Office during major events such as the swearing in of Jeanine Pirro as the interim U.S. Attorney for the District of Columbia in May.
Kirk showed support for Trump for his decision to strike Iran's nuclear facilities in June.
"With the weight of the world on his shoulders, President Trump acted for the betterment of humanity. For the next few hours, spare us the armchair quarterbacking and instead trust our Commander in Chief,” he wrote.
Despite their close relationship, there were times when Kirk seemed to differ with Trump.
In July, Kirk called for the release of files concerning convicted sex offender Jeffrey Epstein and criticized the White House handling of the controversy, but backed off later, saying that he would trust the administration and wanted to move on from the issue.
Kirk's comments came after speaking with Trump, who called Kirk to tell him he still backed Attorney General Pam Bondi. Kirk blasted the DOJ and FBI’s messaging around the Epstein files, calling for transparency.
However, Kirk supported Trump following a Wall Street Journal report that alleged Trump sent a letter to Epstein for his 50th birthday.
-ABC News' Lalee Ibssa contributed to this report.