A fiery crash in Vallejo Thursday morning left a big rig driver dead and a main artery out of Marin County off limits.
A big-rig driver was killed in a dramatic crash that included the man's truck falling off of a highway overpass.
The driver has been identified as William Ballard, 43, from Roseville.
The crash shut down westbound state Highway 37 in Vallejo for three hours Thursday morning, a main artery out of Marin County.
According to the California Highway Patrol, it all started with a collision between an Ace Hardware big-rig and a white pickup truck around 6:40 a.m. on westbound Highway 37 just east of Highway 29.
Late Thursday, investigators said they still don't know what caused the collision, but said when the vehicles collided, they both veered to the right and hit the concrete rail on the right hand shoulder of the overpass.
The barrier was enough to stop the pickup, but the big rig when over the concrete rail and fell 58 feet to the ground below.
The truck landed in a grassy area below and immediately caught fire.
Witnesses said there were several explosions from the products inside the rig.
People who were driving north on Highway 29 said they saw sparks coming from the big-rig before it fell from Highway 37.
Two people, along with an off-duty paramedic, ran to the big-rig as it burned and pulled the driver out of the cabin. Those heroes have asked to remain anonymous.
The big rig driver was taken to a hospital where he was pronounced dead.
The pickup truck's driver was not serious hurt.
The pickup truck, pictured to the right, appeared to have a blown tire, but that could have happened as a result of the impact.
Highway 37 was shutdown for three hours and reopened a little before 9 a.m.
Bay City News contributed to this report.