Secret Service director: Trump rally shooter was identified as 'potential person of suspicion'

The director of the Secret Service says Thomas Matthew Crooks had been identified as a "potential person of suspicion" before the Trump rally shooting.

The head of the Secret Service has revealed that the shooter who tried to kill former President Trump was identified as a "potential person of suspicion," but by the time units were able to track him down, he had managed to open fire at the rally in Pennsylvania. 

United States Secret Service Director Kimberly Cheatle made the remark in an interview that aired on ABC News just hours after Fox News Digital reported that a local law enforcement officer spotted a suspicious man carrying a range-finder just 30 minutes before Saturday’s attempted assassination in Butler. 

That officer reported the sighting to state police, a law enforcement source said. He took a photo, and there was a discussion about whether what he was carrying was a pair of binoculars to try and see the rally better. But then a few minutes into Trump's remarks, the would-be assassin — identified as Thomas Matthew Crooks, 20 — began shooting, according to authorities. 

"I'm being told that the shooter was actually identified as a potential person of suspicion. Units started responding to seek that individual out," Cheatle told ABC News. "Unfortunately, with the rapid succession of how things unfolded, by the time that individual was eventually located, they were on the rooftop and were able to fire off at the former president." 

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Cheatle acknowledged in the interview that responsibility for the security failure that led to the attempted assassination of Trump ultimately rests with herself. 

"The buck stops with me," Cheatle said, adding that "This is an event that should have never happened." 

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Cheatle also told ABC News her first reaction to the shooting was "shock." 

She said the Secret Service was aware of the security vulnerabilities presented by the building Crooks took a sniper's position on to aim at Trump. However, a decision was made not to place any personnel on the roof. 

"That building in particular has a sloped roof at its highest point. And so, you know, there's a safety factor that would be considered there that we wouldn't want to put somebody up on a sloped roof. And so, you know, the decision was made to secure the building, from inside," she said. 

Fox News’ Sarah Rumpf-Whitten contributed to this report.