After Trump assassination attempt, questions swirl about what happened

As the investigation into the assassination attempt on former President Donald Trump intensified Sunday, the U.S. Secret Service was coming under scrutiny as questions mounted on how the alleged gunman managed to fire a barrage of shots from a rooftop with a vantage point of the outdoor Pennsylvania rally stage Trump was speaking from.

The FBI identified the suspected gunman as 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania, whom officials said was armed with an AR-15-style rifle and fired up to eight shots before a Secret Service sharpshooter shot and killed him, law enforcement officials told ABC News.

President Biden, in an Oval Office address, urged calm and unity after the shooting.

"While we may disagree, we are not enemies, we’re neighbors, we’re friends, co-workers, citizens, and most importantly, we are fellow Americans," he said. "We must stand together."

Biden railed against the violence exhibited at the rally and warned "we must not go down this road in America."

Sources briefed on the investigation told ABC News that ahead of the shooting, authorities received reports of a person acting suspiciously and soon spotted the gunman on the roof. An officer tried to make it to the roof but was threatened by the shooter and moments later shots rang out, the sources said. It's unclear whether the information was passed on to Secret Service.

The suspect appeared to be wearing a T-shirt and tan camouflage shorts that blended into the colors of the building he was perched atop.

Watch the ABC News special, "Trump Assassination Attempt Minute by Minute," Sunday at 8 p.m. ET

The firearm recovered at the scene of the assassination attempt was legally purchased in 2013 by the suspect's father, an urgent trace conducted by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) found, according to multiple law enforcement sources.

Kevin Rojek, the special agent in charge of the Pittsburgh FBI office, said a suspicious device was found in the suspect's car and was being analyzed. Another was found in his home and both were rudimentary, according to Rojek.

Federal investigators said they have found no links between the suspect and any international terrorist group. Investigators said they're still looking into whether the suspect had any ties to domestic terrorist groups. Increasingly, the shooting is looking like the action of a lone wolf, sources said.

“At this time, the information that we have indicates that the shooter acted alone and that there are currently no public safety concerns,” Rojek said in a call with reporters Sunday afternoon. “At present, we have not identified an ideology associated with the subject, but I want to remind everyone that we're still very early in this investigation."

'Attack on our democracy'

Also on the call was FBI Director Christopher Wray, who said the assassination attempt on Trump "was nothing short of an attack on democracy and our democratic process."

"An attempt to assassinate a presidential candidate can only be described as absolutely despicable and will not be tolerated in this country,” Wray said.

Rojek said the suspect's gun and cellphone have been sent to the FBI laboratory in Quantico, Virginia, to be analyzed.

Rojek said the suspect's family is cooperating with the investigation and added that the suspect had no known history of mental illness.

In addition to investigating the shooting as an assassination attempt, Robert Wells, assistant director of the FBI's Counterterrorism Division, said the case is also being probed as a potential domestic terrorism act.

The FBI has received more than 2,000 tips on the shooting, Rojek said.

The suspect had no U.S. military affiliation, according to the Pentagon.

Details about alleged shooter emerge

Meanwhile, the Bethel Park Skilled Nursing and Rehabilitation Center confirmed to ABC News on Sunday that the suspect, Crooks, worked at the facility as a dietary aide and that he passed a background check for employment.

"We are shocked and saddened to learn of his involvement as Thomas Matthew Crooks performed his job without concern and his background check was clean. We are fully cooperating with law enforcement officials at this time," said Marcie Grimm, administrator of the center.

Two former high school classmates of Crooks told ABC News that the suspect was rejected from the high school rifle club and asked not to return.

"He didn't just not make the team, he was asked not to come back because how bad of a shot he was. It was considered like, dangerous,” said Jameson Myers, one of the former classmates said. "On the first day of pre-season he basically couldn't even hit the target."

Investigators are also combing through the suspect's social media footprint for clues, officials said.

Investigators are looking at what sources describe as misinformation the suspected gunman appeared to have been recently consuming and whether it played any role in the incident, according to law enforcement sources. So far, investigators have not uncovered any ties to extremist organizations or individuals, though they continue to scour information from the suspect's phone and other digital devices, the sources said.

Trump posted on his Truth Social site that he suffered a bullet wound to his right ear in the attack.

Biden tells nation 'let the FBI do their job'

President Joe Biden and Vice President Kamala Harris were briefed on the investigation Sunday by FBI Director Christopher Wray, Attorney General Merrick Garland, Homeland Security Secretary Alejandro Mayorkas, National Security Advisor Jake Sullivan and U.S. Secret Service Director Kim Cheatle.

Following the briefing, Biden spoke from the White House Situation Room, saying, "We must unite as one nation to demonstrate who we are."

The president said investigators have not determined a motive for the shooting and he requested that Americans not make assumptions on the suspect's motives or affiliations.

"Let the FBI do their job and their partner agencies do their job," Biden said. "I've instructed that the investigation be thorough and swift and the investigators will have every resource they need to get this done."

Biden said he has "been consistent in my direction of the Secret Service to provide him [Trump] with every resource, capability and protective measure necessary to ensure his continued safety."

He said he has also directed the Secret Service to "review all security measures for the Republican National Convention" scheduled to begin on Monday in Milwaukee. He said he has also ordered an independent investigation of the security provided at Saturday's rally.

Biden said he had a "short but good conversation" with Trump late Saturday night, adding, "I'm sincerely grateful that he is doing well and recovering."

Gun shots rang out as Trump began his speech

Trump was less than 10 minutes into his campaign speech and had turned his head to look at a jumbotron when the gunfire began, according to witnesses and video of the moment. Video captured the former president reaching for his ear and going to the ground as multiple shots could be heard.

Sources said Trump underwent a precautionary CT scan after the shooting but everything was clear.

A man who was attending the rally was fatally shot and two other rallygoers were shot and wounded, federal officials said. Pennsylvania Gov. Josh Shapiro identified the deceased victim as Corey Comperatore, 50. The Pennsylvania State Police on Sunday identified the wounded bystanders as 57-year-old David Dutch of New Kensington, Pennsylvania; and 74-year-old James Copenhaver of Moon Township, Pennsylvania. Both are listed in stable condition, according to the state police.

Shapiro said Comperatore, a firefighter and the father of two daughters, died while protecting his family. Shapiro said Comperatore's wife asked him to share that "Corey died a hero, that Corey dove on his family to protect them at this rally."

The FBI is leading the investigation. Overnight, investigators said they executed a warrant at Crooks' home in Bethel Park, about 53 miles south of Butler, Pennsylvania, where the shooting at the Trump rally occurred.

The roof where the suspect fired from had been surveyed during security preparations for the event, a law enforcement source told ABC News.

The roof was empty during those security preparations, the source said.

It remains under investigation why the Secret Service or local law enforcement didn't post someone at the building to prevent anyone from accessing the roof.

Suspicious activity at nearby building

Authorities outside the rally's security perimeter were alerted there was a man acting suspiciously, multiple sources briefed on the probe told ABC News. Local and state police, responsible for security outside that perimeter, began to search for a potential suspect and within minutes found him on the roof of an agriculture building about 400 feet from where Trump was speaking, the sources said.

Butler County Sheriff Michael T. Slupe, who was at Saturday's rally when the shooting broke out, told ABC News that he was informed by other law enforcement that Butler Township police officers were looking for a suspicious person in the area of the rally just before the shooting started.

Slupe said he was told that a Butler Township police officer was vaulted up to the roof where the shooter was located and that the suspect turned and aimed at the officer, who immediately retreated down to the ground and radioed in the gunman's location. Slupe said the gunman then proceeded to open fire on the rally.

It is unclear as of now whether this information was passed along to the Secret Service, responsible and focused for the security of the former president and the crowed inside the security zone.

Butler Township police did not respond to calls for comment from ABC News.

Secret Service denies report it rebuffed Trump team request for beefed-up security

The former president, who was wearing a Make America Great Again hat, was seen in a video clutching his right ear and going to the ground as several Secret Service agents rushed to cover him with their bodies and people in the crowd also ducked for cover.

Anthony Guglielmi, a spokesperson for the Secret Service, posted a statement on X on Sunday disputing media reports that the Secret Service rejected a request from Trump's campaign team to supply additional security resources.

"There's an untrue assertion that a member of the former President's team requested additional security resources & that those were rebuffed. This is absolutely false. In fact, we added protective resources & technology & capabilities as part of the increased campaign travel tempo," Guglielmi wrote.

Some senators call for investigation of Secret Service

"I call on you to launch a full, public and comprehensive committee investigation into this assassination attempt and failures to adequately protect the president," Sen. Josh Hawley, R-Mo., said in a letter released Sunday formalizing a call for the Senate Homeland Security Committee to investigate the attack on Trump.

The House Homeland Security Committee also asked the Secret Service director, Kimberly Cheatle, to testify soon.

Xochitl Hinojosa, spokesperson for the Department of Justice, said in a statement Sunday that Attorney General Merrick Garland has canceled plans to travel to Nevada, Utah and Kansas this week to meet with local law enforcement and speak at the National Bar Association. Hinojosa said Garland will stay in Washington, D.C., to closely monitor the investigation of the attempt on Trump's life.

"The Attorney General continues to receive regular briefings regarding the attack at former President Trump’s rally," Hinojosa said. "This morning he met with Department personnel and partners from across government."

ABC News' Josh Margolin, Pierre Thomas, Luke Barr and Aaron Katersky contributed to this report.