Many questions have been raised about how the police officers and agents tasked with protecting Donald Trump’s rally allowed the gunman to get so close.
Thomas Matthew Crooks was able to climb onto the roof of a building near the outdoor event at the Butler County Fairgrounds, Pennsylvania, where he shot Trump from a distance of 130m (430ft).
The US Secret Service said it has assigned local police to protect the building.
One person in the crowd was killed and two others were seriously injured. Trump suffered an ear injury.
Secret Service spokesman Anthony Guglielmi said his agency had sought help from local police.
He said his agents were responsible for protecting the inside of the fairgrounds, while local police secured the outside area, including the private building used by the gunman.
The local police department referred the BBC’s questions to the state police, who said they were not responsible for the area where the building is located.
A spokesman told the BBC they had provided “all resources” requested by the Secret Service, including 30 to 40 police officers inside the perimeter.
Many observers have questioned why security plans were broken to allow the gunman easy access to Trump.
Crowd members said they spotted the suspect on the roof minutes before the shooting began, while Butler County Sheriff Michael Slupe said a local security officer also spotted the suspect but was unable to stop him.
The police chief admitted there had been a “failure” to secure the facility, but said he believed no one party was to blame.
According to sources cited by CBS News, the BBC’s US partner, and the New York Post, three snipers were posted by authorities inside the building where Crooks fired his shot. These snipers are said to have seen Crooks trying to climb onto the roof.
Jason Russell, founder of Secure Environments Consultants, who worked as a Secret Service agent from 2002 to 2010, including on election campaigns, said the Secret Service often enlists the help of local police when providing security for protests.
“The Secret Service doesn’t have unlimited resources in terms of personnel that can be deployed everywhere,” he told the BBC.
He said agents typically survey campaign event sites days in advance to develop security plans, which they then share with local police agencies.
In this case, he said the building where the gunman was located was outside the official grounds of the event and was under the responsibility of local police.
During the event, he said the communications were shared with all relevant agencies. However, he added that in the “10 seconds” it took for the information to be transmitted, that might have been just enough time for a gunman to fire a few shots.
The roof was known to be a weak point before the incident, NBC News reported, citing two sources familiar with Secret Service operations.
It is possible that agents identified the building as a threat ahead and asked local authorities to place police nearby to prevent access, Mr Russell said.
“For some reason, that didn’t happen,” he said.
One witness, Thomas Gleason, who served 21 years in the US Army as a paratrooper and ranger, said “more security is needed to guard against a long-range threat”.
“Look at the distance and perspective, if someone is going to assassinate [Trump] That would be the most logical shooting point,” he said.
The FBI has since taken over as lead investigator in the case, and the shooting is now the subject of several other investigations by both the House and Senate.
Homeland Security Secretary Alejandro Mayorkas called it a security “failure” and told CNN that “an incident like this cannot happen again.”
U.S. Secret Service Director Kimberly Cheatle said Monday that her agency is working with federal and local police to “understand what happened, how it unfolded, and how we can prevent an incident like this from happening again.”
She added that she would cooperate with any congressional investigation into the shooting.
Cheatle is scheduled to testify before the House Oversight and Accountability Committee on July 22. Republicans on the committee have also called on the Secret Service to produce evidence including internal communications, audio and video recordings, messages sent to local law enforcement, maps, diagrams and pre-event assessments.
