The man killed in a fatal collision between a car and a tractor-trailer Wednesday morning on Highway 101 in Thousand Oaks has been identified as Kunhi Ahn, officials said.

Ahn, 69, a resident of Woodland Hills was on his way to work in Moorpark, when the car he was driving was rear-ended by a big rig driven by Mark Sanders, 49, of South Gate.

Ahn was pronounced dead at the scene at 11:22 a.m., Chief Deputy Medical Examiner, Armando Chavez said.

An autopsy is scheduled this morning to determine the cause of death.

Sanders was not injured.

The California Highway Patrol is investigating the cause of crash that was reported at 11:02 a.m and occurred between the Westlake Boulevard on-ramp and the Hampshire Road off-ramp.

Sanders was northbound on the 101 in the slow lane, or No. 4 lane, when be began to brake as traffic slowed, CHP Officer Brandon Mumme said.

The car, a 2006 Mercedes Benz, appeared suddenly in front of the tractor trailer.

"He doesn't know where the Mercedes came from," Mumme said. "He doesn't know if it came from the on-ramp or the No. 3 lane." The big rig rear-ended the car, pushing it into the lane used to merge onto or exit the highway. The rear of the Mercedes Benz was crushed and its front bumper torn off.

The crash sounded like something falling off of a big truck, said Thomas Ruschke, 24, of Oak Park, who was standing nearby.

"It was a really loud bang," said Ruschke, who had been standing in the sales lot at Nissan of Thousand Oaks in the auto mall on the north side of the highway.

Ruschke ran from the lot and across a small gully to get to the highway to see if he could help. He said another employee from the auto dealer reached the accident scene first, and a number of people who were driving on the highway stopped to help as well.

"It was pretty impressive," Ruschke said of the size of the group that was ready to lend a hand.

The CHP's Mumme said there were two witnesses who could place the tractor-trailer in the fourth lane but they could not give officers more information.

The Mercedes Benz is registered to someone in Woodland Hills, Mumme said, adding that the driver was not the registered owner.

The collision caused northbound traffic to slow, resulting in a backup of cars and trucks which stretched as far back as the Lindero Canyon Road interchange, more than a mile away.

Debris was scattered over the highway's two slower lanes.