The FBI is still trying to determine a motive behind Saturday’s attempt to assassinate former President Donald Trump, while the tone of this week’s Republican convention in Milwaukee likely will be dominated by the violence.

A former fire chief who was killed at Trump’s Pennsylvania rally is being remembered as a “man of conviction.”

The shooting wounded two other men and pierced the upper part of Trumps’ ear with a bullet. The 20-year-old who authorities say carried out the attack is believed to have acted alone with his father’s gun.

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

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Acting Strangely Outside the Event

Officials say Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania — about 50 miles (80 kilometers) from the shooting — first came to law enforcement’s attention when spectators at the Trump rally noticed him acting strangely outside the event. Specifically, he was pacing near the magnetometers, according to a law enforcement official who spoke on the condition of anonymity because they were not authorized to discuss the investigation.

The gunman made it to a nearby roof with an AR-style rifle and a local law enforcement officer climbed to the roof and found Crooks, who pointed the rifle at the officer, Butler County Sheriff Michael Slupe told The Associated Press. The officer retreated down the ladder, and the gunman quickly fired toward Trump.

Trump was showing off a chart of border crossing numbers when the gunfire began.

As the first pop went off Trump said, “Oh,” then raised his hand to his right ear and looked at it before quickly crouching to the ground behind his lectern.

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Someone could be heard near the microphone saying, “Get down, get down, get down, get down!” as agents rushed to the stage. They piled atop the former president to shield him with their bodies as other agents took up positions on stage to search for the threat.

U.S. Secret Service gunmen shot the gunman, officials said.

Trump later said the upper part of his right ear was pierced by a bullet. His aides said he was in “great spirits” and doing well. He arrived in Milwaukee on Sunday evening for the convention, which begins Monday.

A Loner Whose Motive Remains Unknown

Investigators are hunting for clues and the absence of any clear ideological motive so far has led conspiracy theories to flourish.

The FBI said it believes Crooks acted alone. Investigators have found no threatening comments on social media accounts or ideological positions that could help explain what led him to target Trump.

Crooks graduated from Bethel Park High School in 2022. An FBI official told reporters that Crooks’ family is cooperating with investigators.

Crooks’ political leanings 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 Biden was sworn into office.

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Jason Kohler, who said he attended the same high school but did not share any classes with Crooks, said Crooks was bullied at school and sat alone at lunchtime. Other students mocked him for the clothes he wore, which included hunting outfits, Kohler said.

“He was just a outcast, and you know how kids are nowadays,” Kohler told reporters.

Crooks worked at a nursing home as a dietary aide, a job that generally involves food preparation. Marcie Grimm, the administrator of Bethel Park Skilled Nursing and Rehabilitation, said in a statement she was “shocked and saddened to learn of his involvement.” Grimm added that Crooks had a clean background check when he was hired.

Authorities Probe Shooting as Potential Domestic Terrorism

The FBI is investigating the shooting as a potential act of domestic terrorism and questions abounded about how the gunman got so close in the first place.

Kevin Rojek, the agent in charge of the FBI’s Pittsburgh field office, said “it is surprising” the gunman was able to open fire on the stage before the Secret Service killed him.

Bomb-making materials were found inside both Crooks’ vehicle and at his home, officials said. The FBI described the devices as “rudimentary.”

Ex-Fire Chief Who Was Killed Was a “Man of Conviction”

Gov. Josh Shapiro on Sunday said the man killed at the Trump rally, Corey Comperatore, “dove on his family to protect them.”

“Corey died a hero,” the governor said. Comperatore, 50, was a former fire chief.

Pennsylvania State Police identified two other men who were shot as David Dutch, 57, of New Kensington, and James Copenhaver, 74, of Moon Township. Both men remained hospitalized and were listed in stable condition, state police said.

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Comperatore’s quick decision to use his body as a shield against the bullets flying toward his wife and daughter rang true to the close friends and neighbors who loved and respected the proud 50-year-old Trump supporter, noting that the Butler County resident was a “man of conviction.”

“He’s a literal hero. He shoved his family out of the way, and he got killed for them,” said Mike Morehouse, who lived next to Comperatore for the last eight years. “He’s a hero that I was happy to have as a neighbor.”

Randy Reamer, president of the Buffalo Township volunteer fire company, called Comperatore “a stand-up guy” and “a true brother of the fire service.” He said Comperatore served as chief of the company for about three years but was also a life member, meaning he had served for more than 20 years.

“Just a great all-around guy, always willing to help someone out,” Reamer said of Comperatore. “He definitely stood up for what he believed in, never backed down to anyone. … He was a really good guy.”

Trump Arrives in Milwaukee as RNC Goes On

The Republican National Convention starts Monday, with Trump and his advisers pledging resilience in the face of the attack. The four-day event will showcase the former president and his platform as his party formally chooses him to be its nominee.

It was not immediately clear if and how Saturday’s attack would alter the convention, which normally has a celebratory atmosphere. Republican officials have said they want to defy the threat Trump has faced and stick to their plans and their schedule. But at the very least, the event is expected to include a heightened focus on security and a grim recognition of how stunningly close Trump came to losing his life.

The presumptive Republican nominee and his allies will face the nation unquestionably united and ready to “fight,” as the bloodied Trump cried out Saturday while Secret Service agents at his Pennsylvania rally rushed him to safety.

Anger and anxiety are coursing through the party, even as many top Republicans call for calm and a lowering of tensions. As elected officials, politicians and a few regular Americans address the conference, the question is which tone will prevail in the aftermath of the attack: Will it make speeches even more fiery or will calls for calm prevail?