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.

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.

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.

Two sources told ABC News there were what “appeared” to be explosives in the suspect’s found car parked outside the Trump rally. One source said the items looked like grenades. But the sources said they were awaiting forensic results as to whether the items were explosives.

Bomb technicians and other experts were called to investigate. Officials are awaiting confirmation on whether the items contained explosives.

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.

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

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, Briden 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 insure 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."

The president said he plans to address the nation from the White House Sunday night.

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.

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.

Pennsylvania Josh 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.

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.