The man attempted to slow down, striking the driver's side of the Caravan, Sgt. Bob Durham said. He was ejected from his bike and was sent through the middle driver's side window, coming out the other side through the passenger window. The force of the impact then sent the vehicle rolling over on the passenger side and onto the man, police said.
Witnesses nearby rushed to the wreckage and pulled the van off of the motorcyclist before paramedics arrived, police said. The man was taken to Western Medical Center-Santa Ana. He experienced major head trauma and may have been paralyzed, police said. He was put into a medically induced coma due to the severity of his injuries, Lt. Dave Andersen said.
He remained at the hospital Sunday night in critical condition, police said.
"And this all could have been prevented," Andersen said.
Tire tread skid marks just past McCormack indicated the man saw the van pulling out but was unable to slow before colliding with the vehicle, police said.
Police and California Highway Patrol closed down the road to southbound traffic until the afternoon. Traffic exiting the 405 Freeway was redirected north toward South Coast Drive.
The driver of the Caravan was not seriously injured. She remained at the scene and answered a number of police questions but did not wish to speak with the press regarding the accident.
Authorities have not released the name of the motorcycle driver.
KELLY STRODL may be reached at (714) 966-4623 or at kelly.strodl@latimes.com.