Donald Trump was rushed off stage during a rally in Butler, Pennsylvania after a gunman opened fire from a nearby building.
The Republican candidate for president dropped to the ground and was seen with blood on the side of his face. He later said that he heard the whizzing of a bullet, that ripped through his ear.
As the stage was swarmed by secret service agents, he raised a fist into the air and was escorted away.
Rallygoers dropped to the ground as shot rang out, with some then fleeing the area.
One witness told the BBC that he had seen a man with a rifle on the roof of a building moments before Trump was shot at.