(NewsNation) — Local authorities were assigned to cover the building where a man shot a weapon in an attempt to assassinate former President Donald Trump, a U.S. Secret Service source told NewsNation.

The source said it’s standard for local police to handle areas outside the perimeter of an event because they know them better. The shooter was set up on a building some 130 yards away from Trump’s stage at a rally Saturday in Butler, Pennsylvania.

“Secret Service was in charge of this security,” Butler County District Attorney Richard Goldinger confirmed to NewsNation. He said he was not aware of any county units assigned to the building, but it may have been another agency if that’s true. Goldinger added he did not want to get into a finger-pointing match with the Secret Service.

A local officer did check on the roof and found the shooter, Thomas Matthew Crooks, the source said, but did not engage because he couldn’t reach his weapon and Crooks’ gun was pointed at him.

According to the source, the shooter was flagged in the security process as he entered the rally, but officers lost him in the crowd as they tried to follow him. He was then spotted on the roof, and the officer checked on him before backing off. Then, Crooks opened fire. A Secret Service sniper killed him shortly after.

Crooks’ shots injured, but did not kill, Trump and two attendees: David Dutch, 57, and James Copenhaver, 74. Corey Comperatore, 50, was killed as he shielded his family from the fire.

FBI technical specialists successfully gained access to Crooks’ phone, and they are analyzing his electronic devices, the agency said in a statement.

Biden administration response

The Secret Service is still investigating how Crooks got on the roof. White House Press Secretary Karine Jean-Pierre said a motive, as well as the shooter’s affiliations, are still being investigated.

“We unequivocally condemn in the strongest possible terms the violence our nation witnessed that day,” Department of Homeland Security Secretary Alejandro Mayorkas said at a press briefing Monday.

During an appearance on CNN earlier in the day, Mayorkas called the shooting a security “failure.”

Asked about this at the briefing, Mayorkas said “I have 100% confidence in the United States State Secret Service” and its director.

“What you saw on stage on Saturday, with respect to individuals putting their own lives at risk for the protection of another, is exactly what the American public should see every single day,” Mayorkas said.

Both Trump’s Secret Service protection, as well as security at the Republican National Convention, are being enhanced in light of what happened at the rally, Mayorkas said.

Mayorkas could not discuss specifics but told reporters that more personnel, protective resources, technology and capabilities were added. This includes implementing miles of anti-scale fencing, screening, technology and tactical support, he added.

Former USSS agents weigh in

Secret Service snipers at the rally did what they are trained to do Saturday — eliminate the threat, Melanie Burkholder, a former Secret Service agent, said in an interview with NewsNation.

“They would have been placed strategically to have eyes on every part of that arena or venue,” Burkholder said. 

Beth Celestini, who worked for the Secret Service for over two decades before retiring three years ago, said the agency does an “advance” anywhere it is stationed. Depending on the situation, planning can take place weeks or even months in advance, she added.

“The Secret Service always partners with the local law enforcement, state law enforcement,” Celestini said. “We can’t do this job alone. We have to rely on the state and local, and everyone has a job. And I think it’s premature to say exactly what happened.”