Despite the 90-degree heat, thousands descended on Pennsylvania's Butler Farm Show, which is a roughly 100 acre fairground used for agricultural exhibitions. Former President Donald Trump had appeared at the site before.

Butler County voted overwhelmingly for Trump in 2020, so the crowd was expected to be as friendly as you'd find in the country. 

But things took a sudden, deadly turn, minutes after the former president and presumptive Republican nominee began speaking. 

Here's a timeline of the attempted assassination of Trump on Saturday, July 13.

6:03 p.m.: Trump takes the stage; gunman spotted by witnesses

Donald Trump took the stage at 6:03 p.m. local time — about the same time that a man was spotted on the roof of a building about 160 yards, or some 400 feet, away. The man was carrying an AR-style semiautomatic rifle. 

Spectators alerted police, and an armed officer attempted to check the roof.

"We noticed a guy crawling, you know, bear-crawling up the roof of the building beside us, 50 feet away from us," one witness said. "So we're standing there, you know, we're pointing at the guy crawling up the roof."

"He had a rifle — we could clearly see him with a rifle," the witness added. 

The sheriff said one officer tried to reach the gunman but had to fall back.

"All I know is the officer had both hands up on the roof to get up onto the roof," Butler County Sheriff Michael Slupe told CBS Pittsburgh station KDKA, but the officer never made it "because the shooter had turned towards the officer."

"And rightfully and smartfully, the officer let go," Slupe said. After that, the shooter turned his rifle back towards the rally and the crowd and started shooting, Slupe said. 

6:11 p.m.: Three shots are fired, then more shots

As Trump was talking about immigration, the first three shots were fired. They came from Trump's right. Then three more shots were fired, followed by what sounded like an outgoing shot, as the crowd erupted into screams.

Video recorded by a member of the audience shows Secret Service snipers aiming at something in the direction of the gunman. A final shot is heard 15 seconds later.

Secret Service agents surrounded Trump, who was grazed in the ear, as blood ran down his face. It took a minute and a half to get the former president off the stage. 

As Secret Service agents tried to hustle him into his waiting SUV, Trump defiantly raised his fist several times and seemed to say, "Fight." 

Some people in the crowd turned their attention to three others who'd been shot. The victims included 50-year-old Corey Comperatore — a firefighter, father and big fan of Donald Trump. He was shot in the head and killed.

"I asked Corey's wife if it would be OK for me to share that we spoke," Pennsylvania Gov. Josh Shapiro said at a news conference the next day. "She said yes. She also asked that I share with all of you that Corey died a hero, that Corey dove on his family to protect them last night at this rally. Corey was the very best of us. May his memory be a blessing."

Two other people — David Dutch, 57, and James Copenhaver, 74 — were critically wounded. CBS News has learned one of the victims is in a medically-induced coma. 

Trump was taken to a nearby hospital for treatment.

8:13 p.m.: President Biden speaks out against violence

President Biden made a statement in Delaware, where he had been spending the weekend. 

"There's no place in America for this kind of violence," Mr. Biden said. "It's sick. It's sick. It's one of the reasons we have to unite this country. We cannot allow for this to be happening. We cannot be like this. We cannot condone this."

Afterward, Mr. Biden returned to the White House, where he was briefed on the assassination attempt. 

8:42 p.m.: Trump posts he's been shot in his ear

Trump wrote on Truth Social: "I was shot with a bullet that pierced the upper part of my right ear. I knew immediately something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin. Much bleeding took place."

A short time later, he left the hospital, headed to the airport and flew to New Jersey.

1:20 a.m. Sunday: FBI identifies the gunman

Early Sunday morning, the FBI identified the gunman as Thomas Matthew Crooks. He was 20 years old and lived in Bethel, Pennsylvania, about 50 miles from the rally site. He graduated with an associate's degree in engineering science from a community college and worked at a nursing and rehabilitation center. 

So far, investigators say his motive is not known. They say he appears to have acted alone, and they have not found any clear indication of his intentions or threats in his social media accounts.

Investigators throughout the night and morning searched the suspect's home and car. They said they found suspicious devices in his home and vehicle that were rendered safe by bomb technicians.

A former classmate at Bethel Park High School told CBS News that Crooks tried out for the high school's rifle team but failed to make it. Jameson Myers described him as "a normal boy" and a "nice kid who never talked poorly of anyone," and added, "I never have thought him capable of anything I've seen him do in the last few days."

7:36 a.m.: Trump thanks people for their prayers 

Sunday morning, Trump posted a message on Truth Social thanking people for their thoughts and prayers, saying "it was God alone who prevented the unthinkable from happening."

"We will FEAR NOT, but instead remain resilient in our Faith and Defiant in the face of Wickedness," Trump wrote, saying he was praying for the recovery of the people who were killed and wounded in the shooting. 

"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," Trump wrote.

10:21 a.m.: Melania Trump calls the shooter "a monster"

Melania Trump also issued a statement on social media. 

"America, the fabric of our gentle nation is tattered, but our courage and common sense must ascend and bring us back together as one," the former first lady said.

She said that when she watched the "violent bullet" strike her husband, she realized that her life and that of the couple's son Barron was "on the brink of devastating change."

"A monster who recognized my husband as an inhuman political machine attempted to ring out Donald's passion – his laughter, ingenuity, love of music and inspiration," Melania wrote.

2:09 p.m.: Trump says he's going to Milwaukee

Trump confirmed on Truth Social that he was flying to Wisconsin as planned to attend the Republican National Convention, which kicks off Monday.

"Based on yesterday's terrible events, I was going to delay my trip to Wisconsin, and The Republican National Convention, by two days, but have just decided that I cannot allow a "shooter," or potential assassin, to force change to scheduling, or anything else," Trump wrote. 

"Therefore, I will be leaving for Milwaukee, as scheduled, at 3:30 P.M. TODAY," he added.

8 p.m.: Biden delivers Oval Office address

President Biden addressed the nation from the Oval Office Sunday evening.

"We can't allow this violence to be normalized," Mr. Biden said. "The political rhetoric in this country has gotten very heated. It's time to cool it down. We all have a responsibility to do that." 

He added that "politics must never be a literal battlefield, God forbid, a killing field." 

The president cited a number of violent political acts in recent years, including the Jan. 6, 2021, assault on the Capitol, a foiled plot to kidnap Michigan Gov. Gretchen Whitmer, the attack on the husband of former House Speaker Nancy Pelosi, and the intimidation of election officials. 

"In America, we resolve our differences" at the ballot box, Mr. Biden said, "not with bullets."

The FBI says it has received more than 2,600 tips so far. Investigators are now working on that timeline in reverse, from the shooting and all the moments leading up to it, as they dissect the would-be assassin's life in the days and months prior to July 13.

In:
• Trump Rally
• Joe Biden
• Donald Trump