Trump, Biden call for unity after assassination bid stuns US

Rivals Joe Biden and Donald Trump urged Americans to show unity on Sunday after an assassination attempt on the Republican that the FBI said was carried out by a shooter with a legally bought semi-automatic rifle.

The attack put the divided nation on edge in the run-up to the presidential election and was being investigated as a potential act of domestic terrorism, as well as a massive security failure.

President Biden said he would address the nation from the Oval Office later in the day, a step only taken at times of grave crisis, after his 78-year-old predecessor was hit in the ear at a campaign rally in Butler, Pennsylvania.

"Unity is the most elusive goal of all, but nothing is more important than that right now," Biden said in brief remarks from the White House, flanked by Vice President Kamala Harris and his homeland security chief.

The 81-year-old Democrat said he had a "short but good conversation" on Saturday with Trump, his political nemesis whom he regularly brands as a threat to democracy.

Biden said the motives of the shooter, 20-year-old Thomas Matthew Crooks, remained unknown and urged people not to make assumptions about his "affiliations".

A day after being rushed from the stage by Secret Service agents with blood streaked across his face, Trump made a similar call.

"In this moment, it is more important than ever that we stand United," Trump said in a statement on his Truth Social network, adding that Americans should not allow "Evil to win".

The tycoon added that it was "God alone who prevented the unthinkable from happening" and that he would "FEAR NOT".

Trump's wife Melania called the shooter a "monster".

Suspected explosives

Secret Service snipers killed Crooks after he fired multiple shots from a nearby rooftop. A bystander was killed and two spectators critically injured in one of the worst acts of US political violence in decades.

The FBI said that it believed that Crooks acted alone and had no known ideology.

"We located the weapon at the scene, immediately adjacent to the shooter," Kevin Rojek, special agent in charge of the FBI's Pittsburgh field office, told reporters.

"We searched the shooter's car, and we're in the process of searching his phone. During the search of the vehicle, we located a suspicious device, which was inspected by bomb technicians."

Biden said he had ordered a full review of security at the rally, as well as at this week's Republican National Convention in Milwaukee where Trump will be crowned the party's presidential nominee.

Biden praised the victim, named as Corey Comperatore, saying he "was protecting his family from the bullets".

Questions are swirling about shooter Crooks, whose body was seen in television images on a low roof of a building, near a weapon that investigators said was an AR-style semi-automatic rifle legally bought by his father.

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 shocking incident drew immediate criticism of security, particularly about how a presidential candidate could be targeted by a gunman around 150 meters away despite a huge Secret Service detail.

US Secret Service spokesman Anthony Guglielmi rejected "absolutely false" claims that it had refused additional protection for Trump ahead of the rally.

Some phone footage suggested that people had seen the shooter on the roof before he opened fire.

Political fallout

The attempt on Trump's life sent shock waves around the world, but the effects on a tight US presidential race in a deeply divided country are uncertain.

Trump's family has already been promoting images of the president raising a defiant fist to the crowd after the shooting.

His narrow escape has sparked conspiracy theories and finger-pointing by Republicans.

Possible Trump vice presidential pick J.D. Vance claimed Biden's campaign "rhetoric" had "led directly" to the attack.

US politics have become increasingly hostile, with Trump building his image around inflammatory verbal assaults, and many Democrats expressing fury and disgust at Trump's rise.

World leaders expressed outrage over the assassination attempt, with UN chief António Guterres saying he condemned it "unequivocally".