President Joe Biden, a Democrat, ordered a review of how a 20-year-old man with an AR-15-style rifle got close enough to shoot at Trump from a rooftop on Saturday. Trump, as a former president, has lifetime protection by the U.S. Secret Service.

Trump, 78, was holding a campaign rally in Butler, Pennsylvania - a key state in the Nov. 5 election - when shots rang out, hitting his right ear and leaving his face streaked with blood. His campaign said he was doing well.

"That reality is just setting in," Trump told the Washington Examiner on Sunday. "I rarely look away from the crowd. Had I not done that in that moment, well, we would not be talking today, would we?"

Also read: Donald Trump narrowly escapes assassination attempt at Campaign Rally

One person in the crowd was killed and two others wounded before Secret Service agents fatally shot the suspect.

Both Trump and Biden on Sunday sought calm and unity.

Trump is due to accept his party s formal nomination at the Republican National Convention with a speech on Thursday. He pumped his fist in the air several times as he descended the stairs from his plane after arriving in Milwaukee.

"This is a chance to bring the whole country, even the whole world, together. The speech will be a lot different, a lot different than it would ve been two days ago," Trump told the Washington Examiner.

Biden delivered a televised address from the Oval Office in the White House on Sunday.

"There is no place in America for this kind of violence, for any violence ever. Period. No exceptions. We can t allow this violence to be normalized," he said. "The political rhetoric in this country has gotten very heated. It s time to cool it down."

Trump and Biden are locked in a close election rematch, according to most opinion polls including by Reuters/Ipsos. The shooting on Saturday whipsawed discussion around the presidential campaign, which had been focused on if Biden, 81, should drop out following a halting June 27 debate performance.