EMBED >More News Videos Travis Air Force Base officials are investigating a security incident that occurred at the main gate on Wednesday.

TRAVIS AIR FORCE BASE, Calif. (KGO) -- A driver is dead after their car crashed the main gate of Travis Air Force Base. Officials are treating it as a possible attempted attack. The FBI is now leading the investigation."The car basically blew up," said witness Kamren Hernandez. " It was nothing anymore."Hernandez couldn't believe what he witnessed Wednesday night from his family's restaurant just feet from the main gate at Travis Air Force Base -- a black SUV exploding seconds after breaching security gates.Henandez' father, Lamar, saw it too. "It kept exploding -- boom boom. Kept on going."Video posted on Air Force Forum's Facebook page shows military personnel running up to the burning car after it crashed. Firefighters respond and try to put the fire out.A U.S. official tells ABC News it appears the driver had propane tanks in the vehicle, which they may have ignited deliberately."He had something in there explosive," Lamar added. "It sounded like the 4th of July. I've never heard anything like that -- really loud."The driver was killed. Defense officials tell ABC News the driver was a civilian and not a service member."I saw the guy inside, slumped over the passenger seat," Lamar told ABC7 News.The driver has not been identified. U.S. officials say the FBI is treating the case as an act of possible terrorism.