Beaver County SWAT sniper Gregory Nicol said something "didn't seem right" when he first spotted a young man skulking around former President Trump's Butler rally site on July 13.

The team's assistant leader saw the man in the gray T-shirt would-be assassin Thomas Matthew Crooks from his second-floor post inside the AGR complex at the Butler Farm Show, he told ABC News. 

"He was looking up and down the building... it just seemed out of place," Nicol said. 

TRUMP SHOOTING: TIMELINE OF ASSASSINATION ATTEMPT

Trump holds fist

Former President Trump is seen with blood on his face surrounded by Secret Service agents as he is taken off the stage at a campaign event at Butler Farm Show Inc. in Butler, Pennsylvania, July 13, 2024. (Rebecca Droke/AFP via Getty Images)

He noticed an unattended backpack and bicycle, then saw the man pulling a rangefinder from his pocket. At 4:26 p.m., the sharpshooter snapped photos of the bicycle and young man and sent them to a group chat of snipers from his team working the event before reporting the sighting to their command group. 

"I assumed that there would be somebody coming out to, you know, speak with this individual or me. I'll find out what's going on," Nicol said.

Nicol said he tried to shadow the scrawny man in the gray shirt but lost him as Nicol moved down to the AGR building's first level and Crooks was outside the building.

Within two hours, Crooks would fire a volley of shots, injuring the former president and two rallygoers and killing firefighter Corey Compartore. 

PENNSYLVANIA SWAT OFFICER SAYS TEAM HAD NO CONTACT WITH SECRET SERVICE BEFORE TRUMP RALLY SHOOTING

New drone footage shows sight line Trump shooter used to open fire on rally

New drone footage shows the sight line Thomas Crooks used to open fire on the rally. (Fox News)

As the former president began to speak, Nicol noticed rallygoers looking away from the podium and up toward the roof of the building, some shouting that someone was up there. 

Initially he was relieved, thinking that "they must have found this guy we were looking for out there and everybody's watching the police deal with him." 

"That's when I heard gunshots," Nicol said. 

The team described ascending the roof after snipers fired back at Crooks, unsure whether the gunman was dead or alive. 

Thomas-matthew-crooks

Thomas Matthew Crooks is pictured in front of the Butler Fairgrounds in the aftermath of the attempted assassination of former President Trump on July 14, 2024 in Butler, Pennsylvania. (Bethel Park School District/Getty Images)

"So we had access through that ladder, got up onto the roof," said team member Rich Gianvito, whose body camera footage from the rooftop has since been obtained by Fox News Digital. "We're prepared for anything at that point, because at this time, we're unsure."

SWAT medic Michel Vasiladiots-Nicol responded to the roof with Gianvito and other local law enforcement.

"We then ascended that ladder to then meet up with what we weren't sure again if it was a mass casualty or what we were walking into," Vasiladiotis-Nicol said.

There they found Crooks bleeding heavily on the roof, and his wrists were hastily bound with white zip ties in case he was still alive. 

Vasiladiotis-Nicol put her gloved fingers to the shooter's neck, she recalled, and "he had absolutely no pulse."

TRUMP VOWS MORE OUTDOOR RALLIES, SAYS SECRET SERVICE WILL 'SUBSTANTIALLY STEP UP' AFTER ADMITTING FAILURES

Butler Farm Show

Questions about how U.S. Secret Service agents stationed inside the building were able to adequately oversee the rally through small, low-set windows that may not have opened. (Fox News)

Jason Woods, another local sharpshooter, said that their team had no contact with the U.S. Secret Service until after the shooting. 

"We were supposed to get a face-to-face briefing with the Secret Service snipers, whenever they arrived, and that never happened," Woods said. "So I think that that was probably a pivotal point where I started thinking things were wrong because that never happened, and we had no communication with the Secret Service."

In a statement, the U.S. Secret Service wrote that "as it relates to communications on that day, we are committed to better understanding what happened before, during, and after the assassination attempt of former President Trump to ensure that it never happens again." 

"That includes complete cooperation with Congress, the FBI and other relevant investigations," the statement continued.

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Assistant Beaver County SWAT leader Mike Priolo said, "This one is something that we'll always carry with us. I remember standing in the parking lot and talking to one of the guys, and saying we just became part of history and not in a good way."

"I think we all failed that day," Priolo said. "People died. If there's anything that we could have done to stop that, we could have. We should have done."