Butler, Jul 15 (AP) Former President Donald Trump called for unity and resilience Sunday after an attempt on his life added fresh uncertainty to an already tumultuous presidential campaign and raised sharp questions about how a gunman was able to open fire from a rooftop near a Pennsylvania campaign rally.

A full day after the shooting, the gunman's motive was still a mystery, and investigators said they believe he acted alone. President Joe Biden ordered an independent security review of the attack, which left one bystander dead and two others critically wounded. The FBI was investigating the shooting as a potential act of domestic terrorism.

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The attack shook the firmament of the American political system, causing a reassessment and a detente — at least temporarily — of the heated 2024 presidential campaign that has grown increasingly vicious.

Trump, the Republican presidential nominee, said the upper part of his right ear was pierced by a bullet. His aides said he was in “great spirits” and doing well, and he headed to Milwaukee to the Republican National Convention that begins Monday.

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“I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin,” he wrote on his social media site. “Much bleeding took place.”

In a subsequent social post Sunday, Trump said: “In this moment, it is more important than ever that we stand United, and show our True Character as Americans, remaining Strong and Determined, and not allowing Evil to Win."

The rallygoer who was killed was identified as Corey Comperatore, a former fire chief from the area, according to Pennsylvania Gov. Josh Shapiro, who added that Comperatore “died a hero.”

“His wife shared with me that he dove on his family to protect them,” Shapiro said. He declined to discuss the condition of two others who were wounded.

Biden, meanwhile, spoke briefly with Trump and was to address the nation Sunday evening. The president said the country would continue to debate and disagree, but stressed: "We must unite as one nation to demonstrate who we are.”

The FBI identified the gunman as Thomas Matthew Crooks, 20, of Bethel Park, Pennsylvania, which is about 50 miles (80 kilometers) from the scene of the shooting.

The gunman had his father's AR-style rifle and was perched atop a nearby roof when some rallygoers pointed him out to local law enforcement, said two law enforcement officials who spoke to The Associated Press on condition of anonymity to discuss an ongoing criminal probe.

A local law enforcement officer climbed to the roof and found Crooks, who pointed the rifle at the officer. The officer then retreated down the ladder, and the gunman quickly fired toward Trump, the officials said. That's when U.S. Secret Service gunmen shot him, the officials said.

Questions abounded about how the gunman could have gotten so close in the first place. Kevin Rojek, the agent in charge of the FBI's Pittsburgh field office, said "it is surprising” that 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. FBI described the devices as “rudimentary."

His motive remained unclear. Crooks wasn't on the FBI's radar, and he was believed to have acted alone. Investigators are combing through his social media feeds and his home, but so far have not found any threatening writing or posts. His family is cooperating.

Crooks' political leanings were also not 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 as president.

The absence of a clear ideological motive added to the deepening questions about the shooting, denying the public any swift or tidy conclusions about the shocking crime.

Biden urged Americans to stay patient. “I urge everyone — everyone, please, don't make assumptions about his motives or his affiliations," he said. (AP)

(The above story is verified and authored by Press Trust of India (PTI) staff. PTI, India’s premier news agency, employs more than 400 journalists and 500 stringers to cover almost every district and small town in India.. The views appearing in the above post do not reflect the opinions of LatestLY)