US President Joe Biden condemned the assassination attempt on his predecessor Donald Trump in a primetime address from the White House, stating that US politics must never become a “killing field.”

Trump, the presumptive Republican nominee for president, was wounded in the ear after a gunman opened fire at a rally in Butler, Pennsylvania. The attack left one person dead and two others critically injured.

In the Oval Office address—his third as president—Biden urged Americans to “take a step back” and warned that “political rhetoric in this country has gotten very heated.”

“No matter how strong our convictions, we must never descend into violence,” Biden said during his remarks, which lasted just under seven minutes. His short but forceful address went smoothly, despite ongoing scrutiny following several high-profile verbal slips.

In his primetime address, the president called on Americans to come together, warning that increasing political polarization meant November’s election would be “a time of testing.” Biden and Trump remain neck-and-neck in opinion polls ahead of the election.

Speaking from behind the Resolute Desk, Biden listed a series of violent political acts that have occurred in recent years, including shootings targeting congressional members of both parties, the assault on ex-House Speaker Nancy Pelosi’s husband, and the January 6 riots.

“We cannot, must not, go down this road again. We’ve traveled it before in our history,” he said. “In America, we resolve our differences at the ballot box. At the ballot box. Not with bullets.”

The attack on Saturday left America reeling, as Trump was struck in the ear shortly after he began speaking in Butler, Pennsylvania. In images broadcast around the world, the 78-year-old could be seen with blood dripping from his ear and down his face, raising a defiant fist as Secret Service agents pulled him off stage and into a waiting car.

The gunman, identified by the FBI as 20-year-old Thomas Matthew Crooks, was shot dead at the scene by Secret Service agents. Law enforcement agents told CBS News that they discovered explosive materials in his vehicle and at his home. Officials are still investigating what motivated the attack. Crooks was a registered Republican who had previously donated $15 to a liberal campaign group in 2021, according to media reports. Classmates described him as a quiet young man who was bullied throughout school. A local gun club near his home in Pennsylvania confirmed he had been a member.

In his speech, Biden said he was praying for the family of Corey Comperatore, a 50-year-old former firefighter who was shot and killed during the rally, along with two others who were critically injured. Comperatore, a father of two, was killed while shielding his family from bullets as they whizzed past Trump and struck members of the audience. Biden called Comperatore a “hero” who was killed “while simply exercising his freedom to support a candidate of his choosing.”