'I'm supposed to be dead' Trump tells NYP after assassination attempt

Former U.S. president Donald Trump on Sunday told the New York Post he was "supposed to be dead" after surviving an assassination attempt which he described as a "very surreal experience."

"I'm not supposed to be here, I'm supposed to be dead," Trump told the New York Post in an interview aboard his plane en route to Milwaukee for the Republican National Convention where he is set to be confirmed as the party's presidential candidate.

It was a "very surreal experience" he said with a white bandage covering his right ear, the paper said.

"It's time to cool it down. We all have a responsibility to do that," U.S. President Joe Biden said in a televised address following the attack in which Republican Trump was injured in the ear and a bystander was killed by gunfire.

As the country reeled from images of a bloodied Trump waving his fist after the gunman opened fire at a campaign rally in Pennsylvania, Biden added that U.S. politics "must never be a literal battlefield, God forbid a killing field."

The 20-year-old shooter, Thomas Matthew Crooks, was shot dead by Secret Service agents amid scenes of chaos. Authorities say his motive remains unclear.

The FBI said it was investigating the attack as a potential act of domestic terrorism and studying Crooks's phone to discover any "ideologies" he may have had.

Trump said it was "more important than ever that we stand United" and added that Americans should not allow "evil to win," in a post on social media.

Numerous Republicans — who themselves often pose with guns in political ads — have claimed Democrats have promoted extreme rhetoric that led to the shooting.

Trump landed in Milwaukee for the Republican National Convention, during which he will formally be anointed the party's nominee.

The U.S. Secret Service insisted the agency is "fully prepared" to maintain security at the convention, as it comes under severe scrutiny over the attempt to kill Trump.

The agency faces searching questions about how the shooter was able to climb onto a rooftop around 150 meters (500 feet) from where Trump was speaking and fire multiple rounds.

The FBI was "looking at it as a potential domestic terrorism act," the bureau's assistant director of counterterrorism Robert Wells said.

The shooter's father was believed to have bought the semi-automatic weapon used in the attack but it was unclear how the shooter accessed it. Investigators also found a "suspicious device" in the shooter's car.

Crooks's former schoolmates described him as a quiet student who often came across as lonely.

"He was quiet but he was just bullied. He was bullied so much," Jason Kohler, who said he attended the same high school as Crooks, told reporters.

The attack threatens to further inflame tensions at an already febrile moment in the race for the White House.