Local police stationed outside former President Donald Trump's campaign rally in Butler County, Pennsylvania, Saturday peeled off of their traffic posts to assist in the hunt for a "suspicious male" before an officer came face-to-face with the gunman and had to drop from the side of the AGR building, local authorities said Wednesday.

"Upon Former President Trump's arrival, a call went out for a suspicious male near the AGR building and several officers broke free from their traffic intersections of responsibility and responded to the area to aid in the search," Butler Township Manager Tom Knights said Wednesday. "A search was conducted around the AGR building and the person of interest was not located, and no ladder was discovered."

A Butler Township police officer went to check out the rooftop and climbed up with the help of another who "hoisted him up," Knights said. Then he saw the gunman, identified later as Thomas Matthew Crooks, 20, of Bethel Park. Videos show that around the same time, witnesses were screaming that someone had a gun on the rooftop.

FORMER SECRET SERVICE AGENT SAYS TRUMP WOULD-BE ASSASSIN THOMAS CROOKS SCOUTED RALLY SPOT IN ADVANCE

Donald Trump gestures while surrounded by U.S. Secret Service agents

Republican presidential candidate former President Donald Trump gestures while surrounded by U.S. Secret Service agents as he is helped off the stage at a campaign rally in Butler, Pa., Saturday, July 13, 2024.  (AP Photo/Gene J. Puskar)

Crooks aimed his rifle at the officer, Knights said.

"The officer was in a defenseless position and there was no way he could engage the actor while holding onto the roof edge," Knights said. "The officer let go and fell to the ground. Butler Township Police immediately communicated the individual's location and that he was in possession of a weapon. Moments later, the individual commenced firing."

Crooks shot at least four people before snipers from the Secret Service and local law enforcement returned fire. 

EXCLUSIVE TRUMP RALLY VIDEO SHOWS CHAOS AFTER GUNMAN OPENED FIRE

Law enforcement officers stand over the body of would-be Trump assassin, Thomas Crooks on the roof of a building

Law enforcement officers stand over the body of would-be Trump assassin, Thomas Crooks on Saturday, July 13, 2024. The gunman killed at least one person and injured the former president in his attempt. (Todd the Driller)

A Secret Service agent neutralized him at the scene – but not until after he inflicted a fatal wound on Corey Comperatore, a 50-year-old father of two, and critically injured David Dutch, 57, and James Copenhaver, 74.

Trump later revealed he had been hit in the ear and was pictured with blood on the side of his head, raising his fist as Secret Service agents led him off the stage.

The Secret Service secured the scene, and the FBI later took over as the investigating agency.

The FBI was looking into a potential motive and Crooks' recent communications. The Department of Homeland Security's inspector general on Wednesday also announced investigations into the Secret Service's handling of security for the event. 

FORMER SECRET SERVICE AGENT WARNS AGENCY ‘STRETCHED THIN’ WITH NEW RESPONSIBILITIES, LACK OF MANPOWER

Undated file photo of Thomas Matthew Crooks

Undated file photo of Thomas Matthew Crooks. Crooks is alleged to be the shooter in the assassination attempt on former President Donald Trump in Butler, Pennsylvania on Saturday, July 13, 2024. (Obtained by Fox News Digital)

After a congressional briefing Wednesday afternoon, Sen. John Barasso told Fox News' Aishah Hasnie that lawmakers were told Crooks had been identified more than an hour before Trump took the stage.

Sources previously told Fox News Digital that an initial suspicious sighting of Crooks carrying a range-finder before the shooting had been reported to Pennsylvania State Police and "disregarded."

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The PSP countered that it had sent dozens of troopers upon the Secret Service's request to assist in rally security – but they were not responsible for covering the building that Crooks used or the property around it. 

"Butler Township in its entirety has been and will continue cooperating with the investigating agencies and will not be commenting further until the investigation report is complete and made public," Knights said.