The news is likely to further inflame criticism of the Secret Service and its director, Kimberley Cheatle, following days of coverage of security failings leading up to the attack.
A rooftop was left unsecured 150 yards from the rally stage, where 20-year-old Thomas Matthew Crooks was able to take up position with his father’s gun and shoot at Trump.
Security flaws
Bystanders attempted to alert local law enforcement minutes before he opened fire, according to witnesses and video evidence. One said they could not understand why Trump remained on the stage.
Trump, who says the bullet was a “quarter of an inch” away from killing him, has criticised the security flaws in excerpts from a Fox News interview broadcast Monday.
“Nobody mentioned it, nobody said there was a problem. I would’ve waited for 15, they could’ve said let’s wait for 15 minutes, 20 minutes, 5 minutes, something. Nobody said,” he said.
“I think that was a mistake,” he added. “How did somebody get on that roof? And why wasn’t he reported?”
‘Sensitive tactics’
Ms Cheatle, who is under pressure to resign from both Republicans and Democrats, is set to testify before the House of Representatives Oversight Committee on Monday about the assassination attempt.
Alejandro Mayorkas, the homeland security secretary, has said that Trump’s security has been upgraded since the incident, granting him the same level of protection as a sitting president.
He refused to go into details, citing “sensitive tactics and procedures”, but clarified that “personnel and other protective resources, technology, and capabilities have been added”.