PITTSBURGH – After Pennsylvania police leaders revealed there were at least two other suspicious individuals besides would-be assassin Thomas Matthew Crooks spotted at the July 13 Trump rally, experts tell Fox News Digital that reports of “suspicious” or “unusual” people at Secret Service events are common.

Pennsylvania’s State Police commissioner, Col. Christopher Paris, testified before the House Homeland Security Committee this week that at least two other suspicious individuals were identified at the rally before Crooks launched his attempt on the life of former President Trump. 

Actual “threats” are rare, and the gunman is believed to have acted alone. But the state police commissioner’s testimony raised new questions about different aspects of the attempted assassination of Trump.

TRUMP SHOOTER WAS NOT ONLY SUSPICIOUS PERSON AT BUTLER RALLY: PENNSYLVANIA STATE POLICE COMMISSIONER

Paris told lawmakers that before the deadly rally, he asked the Secret Service about a building where Crooks would later climb up and open fire. 

“We were told that Butler [Emergency Services Unit] ESU was responsible for that area, by several Secret Service agents on that walk-through,” he said. County leaders have disputed that statement.

Legislators spent days grilling law enforcement leaders on the rally’s security failures and several have visited the scene, about an hour’s drive north of Pittsburgh, in person. Within days of testifying Monday, U.S. Secret Service Director Kimberly Cheatle resigned.

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Paris testified in front of the House Homeland Security Committee this week that at least two other people had been deemed suspicious in addition to Crooks. The would-be assassin became “even more suspicious” after authorities saw him with a range finder, he said.

“The [counter-sniper] teams were not focused in that area because they believed that the building’s rooftop/roof access was covered. It wasn’t till he started firing that they then turn their attention over there.”

— Bill Gage, retired Secret Service agent

He was also wearing a backpack and moving around outside the perimeter, prompting police to keep an eye on him. Officers approached but he ran off.

“There was a text thread that was going — they took a photo of him at some point when he utilized the range finder,” he told lawmakers. “The suspicion was heightened… I know from an interview that was immediately relayed in the command post to the Secret Service.”

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A person can be flagged as suspicious or unusual for a number of reasons, and the Secret Service has investigators in the field to rapidly assess such an individual, experts say.

“‘Suspicious person’? Not uncommon. Very low bar. ‘Genuine threat’? Much rarer, and Crooks progressed to the latter,” said Paul Mauro, a retired NYPD inspector. 

Crooks was initially seen without a weapon, so authorities deemed him suspicious at that time, but not a full-blown threat, Paris testified.

“They were out looking for him when he began shooting. They were just a few seconds too late.”

— Bill Gage, retired Secret Service agent

“Every single event I worked, which is thousands, there were suspicious people and events that have to be investigated,” said Bill Gage, a retired Secret Service agent and a consultant at Safehaven Security Group.

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Police and the U.S. Secret Service (USSS) also may have differing definitions of what exactly constitutes a suspicious person, he said.

“Why did the director of PSP [Pennsylvania State Police] label them as suspicious? Did they approach an officer and ask for Trump’s autograph? A local might think that’s suspicious, but to USSS it’s kinda normal,” he said. “Or was someone sort of the proverbial long trench coat on a hot day?” 

Gage said that while Paris was forthcoming in his testimony, the answers he gave raise entirely new questions.

“Crooks ‘ran off’ from the officer when confronted? That’s very odd behavior at an event,” he said. “Running from the police and you have a backpack? Was that info relayed to the command post? What was the command post told?”

Gage also wanted to know more about the “text thread” that law enforcement officers were said to be using to communicate regarding Crooks’ initial sighting and disappearance.

OFFICER REPORTED MAN AT TRUMP RALLY WITH RANGE-FINDER 30 MINS BEFORE ASSASSINATION ATTEMPT: SOURCE

“And that Crooks was on the roof for three minutes? Three minutes is an eternity for a sniper,” he said. “The CS teams were not focused in that area because they believed that the building’s rooftop/roof access was covered. It wasn’t till he started firing that they then turn their attention over there.”

For Mauro, the burning question is about where county personnel were stationed as the Secret Service and local partners tried to track Crooks down once action was deemed necessary.

“Did anyone remain in that second floor observation post or not?” he pondered, referring to a vantage point near where Crooks opened fire.

Releasing the operational plan to congressional investigators would help clear up lingering confusion about who was placed where, and why the security breach was allowed to happen, he added.

During her own testimony this week, Cheatle confirmed Crooks had been spotted outside the secure perimeter prior to the shooting and said authorities had been alerted to reports of a suspicious person “somewhere between two and five times.” At another point in her testimony, she said she believed Crooks acted alone.

Crooks was elevated from a suspicious person to an actual threat “seconds before the gunfire started,” she added. Cheatle later stepped down after bipartisan calls for her resignation.

FBI Director Christopher Wray also testified on Capitol Hill, revealing some of the information investigators have been able to glean off of Crooks’ phone and laptop.

Crooks was researching prior presidential assassinations — including by searching Google for the phrase, “how far away was Oswald from Kennedy?” — on the same day he registered to attend the rally.

“Starting somewhere around July 6 or so, he became very focused on former President Trump and this rally,” he said. 

In a statement, the FBI later said the investigation into Crooks was a top priority.

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“Since the day of the attack, the FBI has been consistent and clear that the shooting was an attempted assassination of former President Trump which resulted in his injury, as well as the death of a heroic father and the injuries of several other victims,” a spokesperson said. “This was a heinous attack and the FBI is devoting enormous resources to learn everything possible about the shooter and what led to his act of violence. The FBI’s Shooting Reconstruction Team continues to examine evidence from the scene, including bullet fragments, and the investigation remains ongoing.”

While the 20-year-old failed to kill the GOP presidential candidate, he did kill a bystander named Corey Comperatore, 50, and wound at least two others in the audience, David Dutch, 57, and James Copenhaver, 74. Trump, who ducked for cover and was later pictured with blood on the right side of his head, said he had been struck in the ear.

Trump told Fox News’ “Jesse Watters Primetime” this week that the Secret Service allowed him to walk out on stage without warning him there was anyone suspicious lurking on the outskirts of the rally.

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