BUTLER, Pa. — Former president Donald Trump on Saturday was rushed offstage with blood dripping down his face after a shooting that the authorities called an assassination attempt. One attendee was killed and two others were critically injured at the campaign rally, the Secret Service said, a shocking turn in a tense election season where concerns about violence had already been running high.

During the rally, “a suspected shooter fired multiple shots toward the stage from an elevated position outside of the rally venue,” according to Secret Service spokesman Anthony Guglielmi. The suspected shooter is dead, said Guglielmi, who confirmed the other death and injuries.

Trump, in a social media post Saturday night, said he was shot in his upper right ear and offered his thanks to law enforcement. He also extended his condolences to the families of a person who was shot and killed and another who was injured. A campaign spokesman said the former president was taken to a medical facility but is “fine.”

“It is incredible that such an act can take place in our Country,” Trump wrote on Truth Social.

The scene unfolded just days before he is set to formally receive the GOP nomination for president at the Republican National Convention in Milwaukee — and renewed fears about rising threats of political violence.

At a news conference just before midnight, law enforcement officials said they were still working to determine a motive and were not ready to name the suspect, though they had a tentative identification. FBI special agent Kevin Rojek said investigators consider the shooting an “assassination attempt against our former president Donald Trump.”

Authorities said there would be a lengthy investigation into how the suspect was able to carry out such an attack. Pressed on how the shooter was able to fire multiple times at the venue, Rojek acknowledged: “It is surprising.”

The suspect is a 20-year-old Pennsylvania man, according to a person familiar with the investigation who spoke on the condition of anonymity to discuss it. The alleged shooter used an AR-15-style semiautomatic rifle to carry out the attack, a U.S. official said, also speaking on the condition of anonymity to discuss the early stages of the investigation.

Butler County District Attorney Richard Goldinger said the shooter was on the roof of an office building outside the security perimeter for the event.

Authorities said it was too early to say whether the shooter was acting alone and that they were not ready to release the names of victims, though they said the person killed and the others critically injured were all male adults.

Minutes into his remarks, Trump reached for his right ear and then crouched behind the lectern after the first of several pops, which sent the crowd into a panic. A voice was heard saying, “Get down, get down, get down!” Several more apparent shots followed a couple of seconds later. Audience members screamed, and smoke rose in the air.

Members of Trump’s Secret Service detail rushed in, one yelling, “Hawkeye is here!” as members of the Secret Service’s counterassault team mounted the stage, wearing black tactical gear and pointing rifles at the crowd — trying to give the former president and his detail cover so that agents could rush him to safety.

The crowd roared as Trump and the officers began to maneuver offstage. The former president pumped his fist while walking off with what appeared to be blood dripping down his right ear and streaked across his cheek. A Washington Post photographer observed what appeared to be blood on the riser behind the former president.

Trump’s campaign issued a statement condemning the incident. “President Trump thanks law enforcement and first responders for their quick action during this heinous act. He is fine and is being checked out at a local medical facility,” campaign spokesman Steven Cheung said in the statement. Later in the evening, Trump campaign advisers and Republican Party officials said in a joint statement that Trump looked forward to proceeding with the convention.

At a news conference Saturday evening, President Biden — who was at a church in Delaware during the incident — said he had been briefed and had tried to contact Trump, who he understood to be doing well. “Look, there’s no place in America for this kind of violence. It’s sick,” Biden said. “It’s sick. It’s one of the reasons why we have to unite this country.” Late in the evening, a White House official said Biden and Trump had spoken.

Biden campaign officials said Saturday night that they were working to pull down their television ads as quickly as they could.

Goldinger, the district attorney, said the shooter was on the roof of a nearby office belonging to American Glass Research. William Bellis, chief financial officer at AGR International — which calls American Glass Research a subsidiary and is based in a cluster of buildings closest to the Trump rally — said Saturday night that the company worked with local police beforehand on security concerns. Police blocked off public access to the company’s parking lot, and that space was available for law enforcement use, Bellis said.

Rico Elmore, a former Republican candidate for the Pennsylvania House who spoke ahead of Trump, was feet from the stage when shots rang out. At first, he said it sounded like firecrackers. Elmore, an Air Force guardsman, yelled for people to get down and heard some call for a medic.

About 10 feet from him, to the right of Trump, a man in the audience was bleeding from his head, Elmore said. Before the medical responders could reach the man, Elmore jumped over a barrier and tried to hold the head wound, the blood smearing across Elmore’s white shirt.

“I held his head and keep it in tact but it was just, it was a serious injury,” Elmore said. He didn’t believe the man survived. He said he also saw a woman passed out, but she didn’t appear to be bloodied.

“There was a lot of anger, a lot of fear, a lot of crying. There were a couple people praying,” said Cindy Hildebrand, the chairwoman of the United Republicans of Butler County, who was also at the rally. A woman next to her had a 7-year-old daughter who was up front hanging from a post excited to see Trump. “Now we have a 7-year-old somewhere out there that is just absolutely traumatized.”

As Republicans raised alarms about the vitriol of some opposition to Trump, Hildebrand said her organization received a phone call after the shooting from a woman who said, “He gets what he deserves.”

The crowd evacuated in an orderly manner, some directing anger over what happened at the media. Police told people to leave because the site was an active crime scene.

Dave McCormick, the Republican candidate for Senate in Pennsylvania — who was in the front row — said during an interview on Fox News that he saw a lot of blood and that Trump is “very lucky to be alive.”

Attorney General Merrick Garland said in a statement that he had been briefed on the shooting and briefed the president. The FBI, ATF, U.S. Attorney’s Office for the Western District of Pennsylvania, and the Justice Department’s national security division are working with the Secret Service as other law enforcement agencies, Garland said, adding that “violence like this is an attack on our democracy.”

Pennsylvania Democratic Gov. Josh Shapiro said that he was also briefed on the situation and that state police were at the site. “Violence targeted at any political party or political leader is absolutely unacceptable,” Shapiro said in a statement. “It has no place in Pennsylvania or the United States.”

National and world leaders across the political spectrum quickly weighed in with horror at what unfolded and offered well wishes for Trump.

“There is absolutely no place for political violence in our democracy,” former president Barack Obama said in a statement.

“Political violence has no place in our country,” Senate Majority Leader Charles E. Schumer (D-N.Y.) echoed.

Republicans shared images of Trump fist-pumping toward the crowd.

“God protected President Trump,” wrote Sen. Marco Rubio (R-Fla.), a vice-presidential contender, in a posting with the picture. Another possible running mate, Sen. J.D. Vance (R-Ohio), also shared the photo.

As information about the violence was just beginning to emerge — with authorities saying little about the details of the incident — some Republicans suggested rhetoric from Democrats was to blame. Rep. Mike Collins (R-Ga.) went further: “Joe Biden sent the orders,” he wrote on X.

There is no evidence that Biden was behind the attack.

Sen. J.D. Vance (R-Ohio), a potential Trump running mate, said in a statement on social media that the shooting was “not just some isolated incident.”

“The central premise of the Biden campaign is that President Donald Trump is an authoritarian fascist who must be stopped at all costs,” Vance wrote. “That rhetoric led directly to President Trump’s attempted assassination.”

Republicans preparing for the convention in Milwaukee gathered around televisions in a hotel lobby after the incident. Charlie Gerow, a Pennsylvania-based GOP strategist, was in the hotel and described an emotional scene with people crossing themselves and looking stunned.

The convention is expected to continue but with additional security, according to an official familiar with the preparations who like others spoke on the condition of anonymity to discuss private deliberations.

At a moment when threats against elected officials have escalated, presidential historian Tim Naftali said the tone that Trump and other leaders take in the coming days will have an enormous bearing on what happens next.

Describing the country as a “pressure cooker,” Naftali said: “We’ve been turning up the gas — and some kind of political violence seemed increasingly likely.”

“As a country we have been dancing around Pandora’s box,” said Naftali, who teaches presidential studies at Columbia University’s School of International Public Affairs, “and a horrible person today may have opened it.”

Josh Dawsey, Colby Itkowitz, Maeve Reston, Matt Viser, Joyce Lee, Carol D. Leonnig, Perry Stein, Theodoric Meyer, Alex Horton and Shawn Boburg contributed to this report