President Joe Biden renewed his condemnation of political violence and called for national unity Sunday after an assassination attempt against former President Donald Trump at a political rally in Pennsylvania.

“Disagreement is inevitable in American democracy. It’s part of human nature. Politics must never be a literal battlefield or God forbid, a killing field,” Biden said in a primetime address from the Oval Office Sunday night.

In his remarks, the president referenced or alluded to a number of past cases of political violence, including shootings of Democratic and Republicans members of Congress, the attack on former Speaker Nancy Pelosi’s husband Paul Pelosi and the kidnapping plot against Michigan Gov. Gretchen Whitmer.

“The Republican convention will start tomorrow. I have no doubt they’ll criticize my record and offer their own vision for this country,” Biden said. “I’ll be traveling this week making the case for our record and the vision my vision for the country, our vision. I’ll continue to speak out strongly for our democracy.”

Biden postponed a trip set for Monday to Texas. He was to appear at former President Lyndon Johnson’s presidential library in Austin to mark the 60th anniversary of the Civil Rights Act of 1964. However, the president will be continuing his other travel for the week, including a trip to Las Vegas, Nev.

Earlier Sunday, Biden said he ordered a review of security for the GOP convention, which starts on Monday, and asked for an independent review of security at Trump’s rally, promising to release that review publicly.

Trump, who will be nominated at the convention in Milwaukee to challenge Biden, was speaking to supporters in a key battleground state Saturday evening when several loud pops were heard and he reached for his ear and then ducked to the ground.

With blood running down his face as he was rushed from the stage by his security detail to a waiting SUV, Trump pumped his fist in the air several times and appeared to shout “Fight.” He said later Saturday in a post on TruthSocial, his social media company, that he had felt a bullet rip into his ear.

On Sunday, Trump posted that he had been thinking of delaying his trip to Milwaukee “but have just decided that I cannot allow a ‘shooter,’ or potential assassin, to force change to scheduling, or anything else. Therefore, I will be leaving for Milwaukee, as scheduled, at 3:30 P.M. TODAY.”

Biden said he had spoken with Trump on Saturday night.

“I’m just really grateful that he’s doing well and recovering,” the Democrat said in remarks during the day Sunday in the Roosevelt Room of the White House, flanked by Vice President Kamala Harris and Attorney General Merrick Garland. “We had a short, pretty good conversation. Jill and I are keeping him and his family in our prayers.”

Biden also offered condolences to the family of a rallygoer who died of gunshot wounds when what appears to have been a lone gunman on a roof outside the security perimeter opened fire on the campaign rally in Butler, Pa.

“He was a father. He was protecting his family from the bullets that were being fired. And he lost his life,” Biden said, adding he was praying for the recovery of others who were injured.

“We don’t yet have any information about the motive of the shooter,” Biden said. “We know who he is. I urge everyone, everyone please don’t make assumptions about the his motives or his affiliations.”

The gunman, identified by the FBI as Thomas Matthew Crooks, 20, of Bethel Park, Pa., was killed by Secret Service agents.

The president said he would deliver a national address Sunday night from the Oval Office, but he offered a preview of the theme — which echoed a statement he made Saturday after the shooting.

“As I said last night, there is no place in America for this kind of violence,” Biden said. “An assassination attempt is contrary to everything we stand for as a nation, everything. It’s not who we are as a nation, it’s not America, and we cannot allow this to happen.

“Unity is the most elusive goal of all but nothing is [as] important than that right now. We’ll debate, and we’ll disagree. That’s not going to change. But … we’re going to not lose sight of who we are as Americans,” the Democrat said.

Biden changed his schedule Saturday night and returned to the White House from his beach home in Rehoboth, Del. He said he had recently received a briefing about the shooting from the FBI, which is leading the investigation, and the Secret Service, among others.

Biden said that Trump, as a former president and presumed Republican nominee, was already receiving “a heightened level of security. And I’ve been consistent in my direction of the Secret Service to provide him with every resource capability and protective measure necessary to ensure his continued safety.”

He also said he directed a review of convention security, and asked for an independent review of security at the rally “to assess exactly what happened. And we’ll share the results of that independent review with the American people as well.”