A has been arrested on suspicion of driving under the influence, police said.
Jon Buna was seen driving recklessly in a storage facility parking lot prior to losing his left foot, said Livermore Police Officer Traci Rebiejo.
Buna, 31, on Wednesday went to a storage facility on Rutan Drive, where he had his two-door BMW parked.
Rebiejo said he got into the vehicle and began to drive around the private lot recklessly.
He stopped the car and a frightened female passenger exited the vehicle, Rebiejo said.
What the woman described next to police shows how Buna crashed his vehicle and severed his foot.
The woman told police the driver's door was wide open and that Buna had his left foot hanging down outside the car.
"She thought it looked like he was going to get out of the car," Rebiejo said. "But then she heard the engine rev and it quickly accelerated to about 20 mph in a reversed arch."
The BMW then collided into a parked trailer before hitting a 3-foot safety pole and side-swiping a storage locker door.
Cement cinder blocks that protrude separate the storage units in the lot.
It appears Buna's foot was severed when it became trapped between the cinder block and the vehicle, Rebiejo said.
Buna's foot was completely severed at the ankle, Rebiejo said.
The injured Buna then parked his vehicle back at its parking lot and the woman called for help.