While disagreements are inevitable in American democracy, politics must never become a literal battlefield, said United States President Joe Biden on Sunday while speaking about the assassination attempt on former President Donald Trump.

“We can’t allow this violence to be normalised,” Biden said while addressing his nation from the Oval Office, the formal working space of the US president. “The political rhetoric in this country has gotten very heated. It’s time to cool it down. We all have a responsibility to do that.”

Trump, the Republican Party’s presumptive presidential candidate in elections expected to be held later this year, was injured after being fired upon at a rally in Butler, Pennsylvania, on Saturday.

One spectator was killed while two others were critically injured in the shooting.

The suspected assailant was identified as 20-year-old Thomas Matthew Crooks of Bethel Park, Pennsylvania, who was registered as a Republican voter. He was not an attendee at the rally and was killed by Secret Service agents.

The Secret Service is a federal agency that protects the United States’ top leadership.

Speaking about the shooting on Sunday, Biden said he believes politics should be a place for peaceful debate and not become “a literal battlefield, god forbid, a killing field”.

This came after Paul Abbate, the deputy director of the US’ intelligence and security service Federal Bureau of Investigation, said that the agency had observed increasingly violent rhetoric online since the attack on Trump, reported Associated Press.

“All of us now face a time of testing as the election approaches,” said Biden. “The higher the stakes the more fervent the passions become. This places an added burden on each of us, to ensure that no matter how strong our convictions, we must never descend into violence.”

Biden also noted that the Republican National Convention is scheduled to begin in Milwaukee on Monday. He said he had “no doubt” that Republicans would “criticise my record and offer their own vision for this country”.

He said he would also return to his reelection campaign.

“You debate and you disagree, that is how democracy should run,” said the US president. “You compare and contrast the character of the candidates. The records, the issues, the agenda for America. In America, we resolve our conflicts at the ballot box, not with bullets.”

FBI to probe the incident as ‘potential domestic terrorism’

The Federal Bureau of Investigation on Sunday said that it is probing the shooting as an assassination attempt and potential domestic terrorism.

It added that while its inquiry so far indicates that the shooter acted alone, the federal agency continues to examine if there were any co-conspirators associated with the attack.

“The FBI has not identified a motive for the shooter’s actions, but we are working to determine the sequence of events and the shooter’s movements prior to the shooting, collecting and reviewing evidence, conducting interviews, and following up on all leads,” the agency’s statement read. “We have also obtained the shooter’s telephone for examination.”