The sources described Kazi as a "nomad" and a "vagabond," who lived in many places.
Authorities extracted a video from his cell phone and are analyzing it to try and see if it could help point to a motive. Sources wouldn't offer any details about the video.
The FBI is holding a press conference Friday at 3:30 p.m. and will be asking the public for help and any information about Kazi.
Sources say the information gathered so far still does not point to a concrete motive, with one source calling the man a "mystery" still. Terrorism, mental health issues, and everything else are still on the table as authorities try to uncover a motive.
On Wednesday, the car crashed at 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."
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Hernandez couldn't believe what he witnessed 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.
Hernandez's father, Lamar, saw it too. "It kept exploding -- boom boom. Kept on going."
RELATED: Officials investigate deadly car fire at Travis Air Force Base
Travis Air Force Base officials investigating security incident
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.
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A U.S. official tells ABC News it appears the driver had propane tanks in the vehicle, which may have been ignited deliberately.
The driver was killed. Defense officials tell ABC News the driver was a civilian and not a service member. U.S. officials say the FBI is treating the case as an act of possible terrorism.