Republican lawmakers said they would launch swift investigations into how a sniper apparently managed to evade Secret Service agents and climb onto the roof of a building near where Donald Trump was speaking at an election rally and fire multiple shots before being killed.

The FBI identified 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania, as the “subject involved” in what it termed an attempted assassination in a statement early on Sunday.

Earlier the Secret Service said in a statement that the shooter was dead, one attendee at the rally was killed and two other spectators were injured.

Law enforcement officials told reporters they had not yet identified a motive for the attack.

At least one person interviewed by the BBC said he tried to alert police and the Secret Service, to no avail, to the apparent sniper.

Trump supporters blasted the Secret Service, which has the primary responsibility for protecting Trump as a former US president.

Billionaire ally Elon Musk called for the agency’s leadership to resign.

“How was a sniper with a full rifle kit allowed to bear crawl onto the closest roof to a presidential nominee,” asked conservative activist Jack Posobiec on social media site X.

Republican House of Representatives Speaker Mike Johnson said on social media that the House will have “Secret Service Director KIMBERLY CHEATLE and other appropriate officials from DHS (Department of Homeland Security) and the FBI appear for a hearing before our committees ASAP.”

The Secret Service said shortly after the shooting that it has begun an investigation and briefed Democratic President Joe Biden, Trump’s rival in the Nov. 15 election, though the agency did not immediately respond to additional requests for comment regarding its protocols.

The Pennsylvania State Police referred questions to the Secret Service, which did not immediately respond.

Attendee Ben Maser was outside the rally perimeter, listening to Trump, when he noticed two officers seemingly looking for someone.

Maser, a 41-year-old welder, started scanning the area too.

“I saw the guy on the roof. I told the officer that he was up there. He went about looking for him,” said Maser.

The attack is certain to lead to a review of Trump’s security, and going forward he will likely be provided with a level of protection more akin to a sitting president, said Joseph LaSorsa, a former Secret Service agent who served on the presidential detail.

“There will be an intensive review” of the incident and “there’s going to be a massive realignment,” LaSorsa said. “This cannot happen.”

The Secret Service said in a statement that it had recently added “protective resources and capabilities” to Trump’s security detail, without providing further details.

A retired agent who worked in protective services, speaking on condition of anonymity, said the incident should spark an internal review, and ideally an external one too.

“The gravity of the situation demands thorough scrutiny to prevent such failures in the future and to ensure accountability on all levels,” said the former agent.

SECURING TRUMP RALLIES

During most of Trump’s campaign stops, local police aid the Secret Service in securing the venue.

Agents from other agencies within the Department of Homeland Security, such as the Transportation Security Administration, occasionally help.

It is no easy task. Many Trump rallies feature thousands of audience members, take place in the open air and last for hours.

Before the event, agents scan the venue for bombs or other threats, and Trump invariably arrives in a fortified motorcade.

Law enforcement officials typically put up barriers as a perimeter, and require all attendees to go through a metal detector to enter the venue.

Armed protective agents search all attendees’ bags and even wallets. Many rallygoers are patted down by hand.

Paul Eckloff, a former Secret Service agent who retired in 2020, said agents would have surveyed all the rooftops with a line of sight ahead of time.

“This person either concealed themselves until they became a threat, or were not a threat until they revealed their weapons,” said Eckloff.

In the moments after Trump was injured, the former president was quickly surrounded by Secret Service personnel who formed a human shield, while heavily armed agents in body armor and toting rifles also took to the stage and appeared to scan the area for threats.

Trump was whisked by the agents to a black SUV, and taken to a local hospital, according to the campaign.