U.S. Secret Service snipers spotted Trump rally gunman Thomas Crooks on the roof of the building a full 20 minutes before he began shooting,  top law enforcement officials told House members in an unclassified briefing, Wednesday.

According to ABC News, the briefers, FBI Director Christopher Wray, FBI Deputy Director Paul Abbate, and Secret Service Director Kimberly Cheatle, said Crooks was identified as a person of interest 62 minutes before he attempted to assassinate former President Donald Trump.

They said the the snipers spotted Crooks on the roof at 5:52 p.m.  The would-be assassin was able to fire several shots at Trump at 6:12 pm., grazing the his ear, wounding  two rallygoers, and tragically killing retired fire chief Corey Comperatore.

Crooks was eliminated by snipers 26 seconds after he came within millimeters of killing the GOP 2024 presidential frontrunner. The briefers reportedly said eleven seconds after the first shot, the counter snipers fixed Crook in their sights and 15 seconds after that, he was shot dead.

Sources told ABC News that Crooks made his way to roof of the American Glass Research building by climbing onto the air conditioning unit of an adjacent building and then hopping over.

While Crooks was making his way to his shooting position, Secret Service agents were hearing radio traffic about a suspicious person police were searching for, and more alarmingly, they heard local law enforcement talking about a confrontation involving police.

According to Butler Township Manager Tom Knights, two officers had gone to the lowest point of the building where one officer boosted the other high enough to reach the roof.  Knights said the officer saw the gunman, who turned and pointed his weapon at him.

The officer ducked and fell off the roof, injuring himself.

“The boosting officer and the officer that fell were both on the radio indicating that there was an individual on the roof that did, in fact, have a weapon,” Knights said.

“There was a blanket tactical channel being used. Everyone who was on that tactical channel heard it.”

Incomprehensibly, the building was outside the security perimeter established for the event, leaving the rooftop unmanned. Local police gathered inside the structure, which was reportedly being used as a staging area.

The timeline as briefed by the trio, looks like this:

5:10 Crooks was first identified as a person of interest
5:30 Crooks was spotted with a rangefinder
5:52 Crooks was spotted on the roof by Secret Service
6:02 Trump takes the stage
6:12 Crooks fires first shots

Wray, Abbate and Cheatle also described Crooks’ movements in Butler Township, Pennsylvania, leading up to the moment his was spotted at the Trump rally with a rangefinder.

Briefers told lawmakers Crooks purchased the ammo box at Walmart on July 5, two days after the rally was announced. On July 13, he went to the rally site in the morning, was there for an hour, and then left. He came back sometime in the early 5:00 p.m. hour and tried to enter the perimeter at around 5:30.

Crooks reportedly also purchased a 5-foot ladder at a Home Depot before the shooting, but it was not found at the scene.

Wray, Abbate and Cheatle told lawmakers that after conducting 200 interviews as part of the investigation, they had not been able to identify the shooter’s motive.

House Speaker Mike Johnson and Minority Leader Hakeem Jeffries have reportedly called for a classified briefing with the USSS next week.

Crooks’ presence in the area of the metal detectors in the minutes before the shooting caught the eye of someone in law enforcement who became suspicious and started to approach him, multiple sources told ABC News. At that point, the would-be assassin backed up and faded into the crowd, according to sources. It was not clear how long before the shooting this happened.

Between the time he was spotted near the magnetometers and when Crooks allegedly fired at Trump, there were two sets of radio transmissions, one reporting that police were looking for a suspicious person and another more generic warning that officers were following up on something suspicious, sources said.

The fact that there were local police personnel and counter-sniper units in the AGR building right below Crooks’ position, is being used to explain why Secret Service snipers didn’t take the shot when they first spotted him on the roof.

Investigators, according to ABC News, believe there was “confusion as Secret Service snipers were trying to determine whether there was a threat to Trump and where it might be coming from.” Crooks was reportedly shot dead by “a Secret Service sharpshooter positioned atop a building behind the stage Trump was speaking from at the Butler Fairgrounds.”

Investigators said Tuesday they found a remote transmitter in the suspect’s pocket that may have been intended to set off two suspicious devices found in the suspect’s car and one in his home, according to law enforcement sources. Devices at both locations were similarly constructed in ammunition containers using components including receivers that appear to have been paired with the remote control found in the suspect’s pocket, sources said.

The receivers in each device were connected to a series of components that investigators say met the “eye test” — having parts present that could have made viable explosives, although the functionality of the devices is still being determined. The purpose of the devices is also unknown. Whether they were intended to cause a significant blast to hurt people or if they were designed to create smoke, fire and a low-grade blast for a diversion is unclear.

Investigators also found a tactical vest in the suspect’s car, though it is unclear why he did not wear it during the assault on the former president’s rally. Some investigators are wondering whether he anticipated dying in the attack.

The shooter also asked his employer if he could take a day off on Saturday but said he would return to work perhaps as soon as Sunday, the day after this attack, according to law enforcement sources. But thus far, investigators have turned up nothing to suggest that he had any accomplices or other support to carry out his deadly objective.

“I don’t have all the details yet, but it was a very short period of time,” Cheatle said. “Seeking that person out, finding them, identifying them, and eventually neutralizing them took place in a very short period of time, and it makes it very difficult.”

ABC News also reported that Secret Service had requested a local police cruiser to be positioned at the AGR building, but local police officials did not provide one.