The driver said he was certain it was a bear because the animal rolled up onto his windshield. But then, according to the driver, the bear recovered, got up and ran away.
The bear was last seen jumping the 126 Freeway perimeter fence.
Police say the driver stayed in the area looking for the bear but couldn't locate it.
The California Highway Patrol and Animal Control were notified.
Officials said the bear may be injured and in need of medical assistance. They also said the injury could make the bear very dangerous.
If you spot a bear, police advise you not to approach it. Instead, call 911, or call the Ventura Police Department at (805) 339-4400.