The political leanings of Crooks were not immediately clear. Records show Crooks was registered as a Republican voter in Pennsylvania, but federal campaign finance reports also show he gave $15 to a progressive political action committee on Jan. 20, 2021, the day President Joe Biden was sworn in to office.

The U.S. Secret Service is investigating how a gunman armed with an AR-style rifle was able to get close enough to shoot and injure former President Donald Trump at a rally Saturday in Pennsylvania, a monumental failure of one the agency’s core duties.

The gunman, who was killed by Secret Service personnel, fired multiple shots at the stage from an “elevated position outside of the rally venue,” the agency said.

An Associated Press analysis of more than a dozen videos and photos taken at the Trump rally, as well as satellite imagery of the site, shows the shooter was able to get astonishingly close to the stage where the former president was speaking. A video posted to social media and geolocated by the AP shows the body of a man wearing gray camouflage lying motionless on the roof of a manufacturing plant just north of the Butler Farm Show grounds, where Trump’s rally was held.

The roof was less than 150 meters (yards) from where Trump was speaking, a distance from which a decent marksman could reasonably hit a human-sized target. For reference, 150 meters is a distance at which U.S. Army recruits must hit a scaled human-sized silhouette to qualify with the M16 assault rifle in basic training. The AR-15, like the shooter at the Trump rally had, is the semi-automatic civilian version of the military M16.

The Secret Service didn’t have anybody at a late-night news conference where FBI and Pennsylvania State Police officials briefed reporters on the shooting investigation.

FBI Special Agent in Charge Kevin Rojek said it was “surprising” that the gunman was able to fire at the stage before he was killed.

Members of the Secret Service's counter sniper team and counter assault team were at the rally, according to two law enforcement officials. The officials spoke on condition of anonymity because they weren’t authorized to discuss details of the investigation.

The heavily-armed counter assault team, whose Secret Service code name is “Hawkeye,” is responsible for eliminating threats so that other agents can shield and take away the person they are protecting. The counter sniper team, known by the code name “Hercules,” uses long-range binoculars and is equipped with sniper rifles to deal with long-range threats.

U.S. Secretary of Homeland Security Alejandro Mayorkas said his department and the Secret Service are working with law enforcement to investigate the shooting. Maintaining the security of presidential candidates and their campaign events is one of the department’s “most vital priorities,” he said.

“We condemn this violence in the strongest possible terms and commend the Secret Service for their swift action today,” Mayorkas said. “We are engaged with President Biden, former President Trump and their campaigns, and are taking every possible measure to ensure their safety and security.“

Calls for an investigation came from all sides.

The FBI said it will lead the investigation into the shooting, working with the Secret Service and local and state law enforcement.

Attorney General Merrick Garland said the Justice Department "will bring every available resource to bear to this investigation.”

“My heart is with the former President, those injured, and the family of the spectator killed in this horrific attack,” Garland said in a statement. “We will not tolerate violence of any kind, and violence like this is an attack on our democracy."

Trump lands in New Jersey, Biden back at White House

Trump’s private jet landed shortly after midnight Sunday at Newark Liberty International Airport.

Video posted by an aide showed him deplaning flanked by U.S. Secret Service agents and heavily armed members of the agency’s counter-assault team, an unusually visible show of force by his protective detail.

Trump planned to spend the night at his private golf club in nearby Bedminster, New Jersey.

Meanwhile, President Joe Biden arrived at the White House early Sunday after cutting short a weekend trip to Rehoboth Beach, Delaware.

The White House said he would receive a briefing from Homeland Security and law enforcement officials on the attempted assassination of Trump later in the morning.

Vice President Kamala Harris was also to attend.