US investigators have identified a 20-year-old man as the suspect involved in the shooting of former President Donald Trump at a rally in the eastern US state of Pennsylvania.

Trump sustained an injury on his right ear when a bullet was fired during his speech at Saturday's rally.

One attendee was shot dead and two others were seriously wounded.

The Federal Bureau of Investigation said in a statement on Sunday that the FBI has identified Thomas Crooks in Pennsylvania as the subject involved in the attempted assassination of the former president.

The suspect was shot dead at the scene.

ABC News and other major US media outlets have reported that Crooks used an AR-15-style rifle which was legally purchased by his father.

The media reported that the suspect was registered as a Republican voter but whether he had a link with extremist groups is unknown.

The AP news agency has quoted law enforcement officials as saying that bomb-making materials were found inside the suspect's vehicle and at his home.

President Joe Biden said at a news conference on Sunday, "The FBI is leading this investigation, which is still in its early stages."

He said, "We don't yet have any information about the motive of the shooter."

The shooting incident sent shockwaves across the US. Attention is focused on how it could impact the upcoming presidential race.