What we know about the attempted assassination at Trump rally in Butler, Pa.

Former President Donald Trump had just begun his remarks at a campaign rally in Butler, Pa., Saturday evening when a series of gunshots rang out, followed by screams.

Secret Service agents rushed toward Trump and soon whisked the former president, whose face and right ear were bloodied, from the stage. Trump, who later reported he was shot in the ear, was said to be “fine” and safe, and was being treated for his injuries.

Two people were killed, including the suspected shooter, and two rally attendees were injured, according to the Secret Service and the FBI.

The shooting comes amid a presidential campaign that has sharply divided the nation over volatile issues including gun violence, the right to carry firearms, and women’s reproductive rights, and while President Joe Biden’s campaign is mired in conflict, as some Democratic members of Congress call on him to quit the race.

Here’s what we know and don’t know.

Trump, the Republican presidential candidate, had just taken the stage at a campaign rally at the Butler Farm Show in Butler, and was early in his remarks when a series of gunshots sounded at 6:11 p.m. Trump winced and grabbed his right ear and then crouched down behind the podium as rally attendees screamed and members of the Secret Service rushed toward him as more shots were then heard.

» READ MORE: FBI probing motives, background of Thomas Matthew Crooks, the Western Pa. gunman behind Donald Trump assassination attempt

Soon after, a Secret Service agent or a first responder yelled that “shooter is down.” Secret Service agents then helped Trump stand up. His right ear appeared bloody and there were streaks of blood on his right cheek.

Corey Comperatore, a 50-year-old firefighter and enthusiastic Trump supporter from Sarver, Butler County, was killed when shots broke out at the rally and he shielded his wife and daughters, according to Gov. Josh Shapiro and a Facebook post by his sister.

» READ MORE: Corey Comperatore identified as man killed in Trump rally shooting

Pennsylvania State Police identified the two people injured as David Dutch, 57, of New Kensington, and James Copenhaver, 74, of Moon Township. Both were hospitalized in stable condition Sunday.

A spokesperson for Trump, 78, said he was “fine” and, after being treated at a local medical facility, flew to his golf club in Bedminster, N.J.

In a statement posted on Truth Social Saturday night, Trump said he “was shot with a bullet that pierced the upper part of my right ear. I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin. Much bleeding took place, so I realized then what was happening.”

Sunday morning, Trump issued a call for unity on Truth Social: “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 FBI identified Thomas Matthew Crooks, 20, of Western Pennsylvania, as the alleged shooter.

Crooks resided in Bethel Park, a suburb of Pittsburgh in Allegheny County, according to public records. Bethel Park borders Butler County, where Trump’s rally took place.

Crooks was a registered Republican, according to the voter roll.

He was wearing a T-shirt from a popular YouTube channel that focused on firearms and explosives at the time of the would-be assassination.

Crooks had no identification on him at the time of the shooting, Kevin Rojek, special agent in charge of the FBI Pittsburgh office, said during a news conference early Sunday morning.

» READ MORE: Why Thomas Matthew Crooks tried to assassinate Donald Trump is a mystery to investigators and his ex-classmates

The shooter was just outside the grounds of the rally on a roof and, therefore, would not have passed through magnetometers that were set up to screen rally attendees, authorities said.

The U.S. Secret Service shot and killed him.

“There’s going to be a long investigation into exactly what took place and how the individual was able to get access to the location,” Rojek said.

» READ MORE: The Secret Service is investigating how a gunman who shot and injured Trump was able to get so close

”We do not have an identified motive,” Rojek said. But he called the shooting “an assassination attempt” against Trump.

Authorities said Crooks used an AR-15-style rifle, which was recovered Saturday at the scene. Two law enforcement officials told The Associated Press investigators believe the weapon was bought by Crooks’ father six months ago. The AP also reported bomb-making materials were found inside Crooks’ vehicle and at his home.

Bivens said there is “no reason to believe there’s any other existing threat” but an investigation continues.

The FBI is leading the investigation into the attempted assassination of Trump, and the state police is investigating the other shootings, including the homicide.

“We did not have any specific threat information,” Rojek said.

But just before the shooting, people in the audience told local police about a man climbing to the roof of a nearby building, the Associated Press reported Sunday, citing two law enforcement officials. One local police officer climbed to the roof and encountered Crooks, who pointed his rifle at the officer, the AP reported. That officer climbed down the ladder and Crooks took a shot at Trump, according to the AP.

Pennsylvania State Police and FBI officials said they were not prepared to make such a conclusion while the investigation is in its early stages. “This is a tragic incident that occurred,” Bivens said. “Just know it will be thoroughly investigated.” Rojek called it “surprising” that a sniper was able to fire off several shots at such a security-heavy event.

U.S. Rep. Scott Perry (R., Pa.), a member of the House Oversight Committee, pledged a full probe of security surrounding the rally in the coming days.

“America wants answers — without delay, drama, or games — and our leaders need to provide those … without delay, drama, or games,” he said in a statement.

In a brief news conference Saturday night, Biden called the shooting “sick” and condemned all political violence.

“There’s no place in America for this kind of violence,” Biden said. “It’s sick, it’s sick. We have to unite this country. We cannot allow this to be happening.”

The president said he was “grateful to hear” that Trump is safe “and doing well. I’m praying for him and his family and for all those who were at the rally.”

In a prime-time address to the nation from the Oval Office Sunday night, he called on Americans to recommit themselves to using peaceful political rhetoric and striving for national unity. “There is no place in America for this kind of violence, or for any violence, ever. Period. No exceptions,” Biden said. “We cannot allow this violence to be normalized.”

Pennsylvania Gov. Josh Shapiro said, in part: “Violence targeted at any political party or political leader is absolutely unacceptable. It has no place in Pennsylvania or the United States.”

New Jersey Gov. Phil Murphy posted on X, formerly known as Twitter: “Please pray for President Trump, everyone at the rally, and our country. God Bless America.”

Sen. John Fetterman (D., Pa.) said Trump being shot was “a dark day for our nation” and called for political unity in the country. “We just have to turn down the temperature,” Fetterman said during an interview on CNN Sunday.

Philadelphia Mayor Cherelle L. Parker said: “Violence has no place in American politics.”

» READ MORE: GOP delegates from Pa. prepare to give Trump a ‘hero’s welcome’ in Milwaukee

Melania Trump issued a statement Sunday saying in part: “When I watched that violent bullet strike my husband, Donald, I realized my life, and Barron’s life, were on the brink of devastating change.”

Archbishop of Philadelphia Nelson Pérez condemned the shooting, and violence in all forms. “Working together, we can resolve our differences through peaceful dialogue and conquer the sin of hatred,” Pérez said.

» READ MORE: 'Conquer the sin of hatred': Turning to prayer after Trump rally assassination attempt

Butler, a city of a little over 13,000 as of the 2022 census, is the capital of Butler County. It is 35 miles north of Pittsburgh.

The Republican National Convention is slated to begin Monday in Milwaukee, where Trump is anticipated to be named the party’s presidential nominee. The convention is expected to proceed as scheduled. It is not clear if additional security measures will be in place.