Officials are demanding to know how an armed man was able to get to the top of a building and shoot former President Donald Trump. A report of a suspicious man had reached police and witnesses pointed and shouted at an armed man on a roof nearby where Trump was speaking.

The attempted assassination left Trump and two other men wounded. A former fire chief, 50-year-old Corey Comperatore, was killed while protecting his family. Investigations will be launched in Congress — in addition to a review ordered by President Joe Biden.

Here's a look at what we know so far about the attempt on Trump's life and its aftermath:

Police had clues that something was amiss before the shooting

Spectators at the Trump rally noticed a man later identified as Thomas Matthew Crooks Crooks pacing outside the event's metal detectors. Police had received reports of his behavior. Witnesses later pointed and shouted about the man with an AR-style rifle on the roof.

It was a Butler Township police officer who encountered the gunman on the roof before the shooting. The officer was looking for the suspicious person when another officer hoisted him up so he could grab the edge of the roof.

The officer then dropped down to the ground, injuring his ankle. A sniper killed Crooks seconds after he fired toward the former president.

Shooting followed 'Absolute and abysmal failure' on part of Secret Service, expert says

At least a dozen police officers and sheriff's deputies were assisting the U.S. Secret Service and Pennsylvania State Police with rally security.

Stan Kephart, a former police chief who worked event security for two former presidents, said the shooting followed an "an absolute and abysmal failure" on the part of the Secret Service to protect Trump. The agency is ultimately responsible for the candidate's safety, he added.

"You don't get to blame other people. They are under your control," said Kephart, now a consulting expert on law enforcement event security.

Elected officials launching multiple investigations

President Joe Biden has ordered an independent investigation of the assassination attempt including security at the rally. Homeland Security Secretary Alejandro Mayorkas said he has "full confidence" in the Secret Service's leadership, but he conceded that the gunman never should have reached that deadly position.

Congressional committees also moved to investigate, also saying they were alarmed at how the would-be-assassin was able to open fire from a rooftop within 135 meters (147 yards) of the former president.

The first hearing has been scheduled for July 22 with the director of the Secret Service, Kimberly Cheatle, set to testify. She'll speak before the House Committee on Oversight and Accountability.

FBI investigating the attack as a potential act of domestic terrorism

The FBI said it was investigating the attack as a potential act of domestic terrorism, but the agency has not identified a clear ideological motive. The FBI believes Crooks, who had bomb-making materials in the car he drove to the rally, acted alone with a gun purchased by his father.

The FBI said Monday that analysts had gained access to the shooter's phone, though a law enforcement official who was not authorized to discuss the matter publicly and spoke on condition of anonymity said the device has not revealed meaningful information about any potential motive.

The official also said that investigators believe Crooks purchased 50 rounds of ammunition on the day of the attack.

The FBI has conducted nearly 100 interviews of law enforcement officials, attendees at the rally and other witnesses, and it has received hundreds of digital media tips.

Trump, with bandaged ear, appears at convention

Two days after surviving an attempted assassination, the former president appeared at the Republican National Convention's opening night on Monday with a bandage over his right ear.

GOP delegates cheered wildly when Trump appeared onscreen backstage and then emerged in the arena, visibly emotional, as country star Lee Greenwood sang "God Bless the USA." That was hours after the convention had formally nominated Trump to head the Republican ticket in November against President Biden.

Trump, accompanied by a wall of Secret Service agents, did not address the hall but smiled silently and occasionally waved as Greenwood sang. He eventually joined his newly announced running mate, Ohio Sen. JD Vance, to listen to the night's remaining speeches.

The convention resumes Tuesday, when the focus shifts to immigration, an issue central to Trump's political brand that helped endear him to the GOP base when he began his first campaign in 2015.