"We know that he [Trump shooter Thomas Crooks] fired at least eight because we recovered eight cartridges on the roof," Wray said during a US House Judiciary Committee hearing.
Wray added that the collapsible stock of the weapon used in the shooting at a Trump rally may have made it less visible to the crowd.
The shooting took place on July 13 at a Trump rally in Butler, the US state of Pennsylvania. Trump sustained a gun wound to his right ear and was briefly hospitalized. Thomas Crooks, 20, killed a member of the audience and injured two others in the crowd before the Secret Service neutralized him.
The FBI is investigating the incident as an assassination attempt and potential domestic terrorism.