President Biden condemned political violence in remarks from the Oval Office on Sunday, and said the attempted assassination of former President Donald Trump necessitates a cooling down of heated political rhetoric in the country. 

“I want to speak to you tonight about the need for us to lower the temperature in our politics,” Biden said. “We’re neighbors or friends, coworkers, citizens. Most importantly, we are fellow Americans, we must stand together,” Biden said.

Biden drew a throughline from the Jan. 6 attack on the Capitol to the assault former Speaker Nancy Pelosi’s husband and intimidation of election officials: “We can’t allow this violence to be normalized,” Biden said. “I believe politics ought to be an arena for peaceful debate.”

“Our politics must never be a literal battlefield,” he said. “We resolve our differences at the ballot box — not with bullets.”

The attempted assassination of former President Trump is being investigated as Trump prepares to officially accept the Republican party’s presidential nomination at its convention in Milwaukee this week.

On Saturday, a 20-year-old identified as Thomas Matthew Crooks allegedly shot at Trump and killed one person at a political rally for the former president in Butler, Pa.

Trump said a bullet pierced the top of his right ear. 

Biden’s remarks from the Oval Office on Sunday night capped a day marked by drips of information revealed about Crooks and his victims, one of whom was killed.

FBI officials described Crooks as a lone gunman with no obvious political ideology. On Capitol Hill, the shooting spurred increased scrutiny of the Secret Service and whether it did enough to protect Trump, but also raised widespread concerns about political violence.

Biden has ordered an independent review of the national security measures in place at Trump’s rally, and promised to release the results of that investigation publicly.

Security ramps up at the RNC convention

The Trump campaign said security is being stepped up around the site of the Republican National Convention in Milwaukee, which kicks off on Monday. The RNC, already a high security event, is drawing guests from across the country to join the proceedings to formally nominate former President Donald Trump as the Republican Party candidate for president.

Trump arrived in Milwaukee on Sunday after saying that the threat to his life a day earlier would not postpone his plans.

“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 said in a post on Truth Social.

At the event, Trump is expected to accept his party’s nomination for president and name his running mate week’s there. His speech is planned for Thursday.

Biden, after speaking briefly with Trump on Saturday night, said he’s “sincerely grateful that he’s doing well and recovering.”

Biden also said he’s ordered the Secret Service to provide Trump with “every resource, capability and protective measure necessary to ensure his continued safety,” and in addition has asked the agency to review all security measures in place for the Republican National Convention.

Officials from the city of Milwaukee, the Secret Service and FBI said their security plan for the Republican National Convention will remain in place.

“We’re not anticipating any changes to our current security footprint or planning,” said Audrey Gibson-Cicchino, the RNC coordinator for the U.S. Secret Service.

FBI Special Agent in Charge Michael Hensle said the bureau is investigating the chatter that has bubbled up since the shooting Saturday, but said there was “no known articulated threat against the RNC” or any attendee.

Milwaukee Police Chief Jeffrey Norman reiterated that coordination was happening between the city and federal officials. He said the police department was “very comfortable” with the current plans.

“We got this,” he said. Norman emphasized the police department’s commitment to protecting not just convention attendees, but also city residents. “This is our community, too,” Norman said.

Where the investigation stands

The FBI is looking into Crooks’ actions in the days and weeks before the shooting, as it leads the investigation into the assassination attempt.

The bureau said it was investigating the incident as “an act of domestic terrorism,” but had not yet identified an ideology associated with the shooter. Investigators say they believe he acted alone but have not yet established a motive.

Key evidence collected from the scene includes an AR-style 556 rifle, which was purchased legally, and Crooks’ cell phone, said Kevin Rojek, special agent in charge of the FBI’s Pittsburgh field office.

“Our primary focus is on the phone and we’re working to get access to the phone,” Rojek said.

Investigators said they had limited insight into recent communications that Crooks made.

Crooks’ family is cooperating with the investigation. His father purchased the weapon used in the attack and investigators are looking into how Crooks gained access to it.

Also being analyzed is a device found in Crooks’ car. FBI officials said the device was “rudimentary” in nature.

There was no indication that Crooks had mental health issues and investigators found no threatening language on his social media accounts.

Attorney General Merrick Garland said he’s “grateful that former President Trump is safe following yesterday’s horrific assassination attempt.” FBI Director Christopher Wray called the attack “absolutely despicable.” 

Congress to investigate attack

Sen. Gary Peters, D-Mich., chair of the Senate Homeland Security Committee, plans to launch an investigation into the assassination attempt, an aide confirmed to NPR. Peters is also running the Senate Democrats’ 2024 campaign operation.

The attack has renewed concerns about threats to lawmakers.

House Republicans received a briefing from top law enforcement officials on Capitol Hill Sunday afternoon, according to a source granted anonymity to discuss security matters. The agencies included the House Sergeant at Arms and U.S. Capitol Police. A separate source confirms that House Democrats will receive a similar briefing Monday at 2 p.m.

The briefings are part of a broader concern among lawmakers about an uptick in threats against members, staff and their families. Congress has been debating additional funding for member security since the Jan. 6 riot at the Capitol and a subsequent wave of threats that have continued.

The other victims

Corey Comperatore, a 50-year-old father and firefighter from Sarver, Pa., was identified by state officials as the man killed in Saturday’s attack.

During a news conference, Pennsylvania Gov. Josh Shapiro said that he spoke to Comperatore’s wife, who described him as a “girl dad” and a firefighter who went to church every Sunday; a man who loved his community and his family. Comperatore, Shapiro said, was an avid supporter of Trump and was “so excited to be with him last night in the community.”

President Biden offered his condolences to his family after they said Comperatore died shielding them from the bullets.

“He was a father, who was protecting his family from the bullets that were being fired,” Biden said. “And he lost his life, God love him.”

Two other Pennsylvania residents who were injured in the shooting — David Dutch, 57, of New Kensington and James Copenhaver, 74, of Moon Township — were both hospitalized and in stable condition on Sunday.

NPR’s Carrie Johnson and Ryan Lucas contributed to this story.