DUBLIN — A bicyclist died Friday afternoon in unincorporated Contra Costa County after he was struck by a car and pinned underneath.

The driver of the car then suffered major injuries when she swerved into oncoming traffic and was struck by a sport utility vehicle, according to the California Highway Patrol.

The collisions occurred at 5:10 p.m. in the 8600 block of Camino Tassajara, just 50 feet from the Alameda County line.

The adult bicyclist was headed south on the road when he was struck from behind by a green Honda Accord, driven by a 40-year-old Cupertino woman.

According to CHP Lt. Lorraine Krolosky, the woman lost control of her car, pinning the bicyclist underneath as she swerved into oncoming traffic and was struck by a northbound gray Range Rover.

The bicyclist, who was not immediately identified, was declared dead at the scene.

The woman suffered major injuries and was taken by helicopter to John Muir Medical Center in Walnut Creek. The Range Rover driver, a Danville man in his 30s, had minor injuries.

The cause of the accident remains under investigation, though alcohol and drugs are not believed to be a factor, according to the CHP.

"I witnessed the man flying vertically through the air," said John Kincaid, who was driving northbound two vehicles behind the SUV and the saw the collision in front of him. "The driver of the Range Rover looked stunned."

He said the victim appeared to be in his 30s.

There was substantial commute traffic in both directions at the time, Kincaid said. Several people stopped and began calling 9-1-1. Some people received a busy signal, he said, and it took about 20 minutes for medical personnel to arrive.

Some people, anxious to get through the crash site, kicked pieces of the victim's bicycle out of the way as they passed, Kincaid said.

The crumpled bicycle was found in the southbound lane when a reporter arrived at the scene. The Honda's air bags had deployed and there was major front end damage to the car which faced the Range Rover in the northbound lane.

Reach Roman Gokhman at 925-945-4780 or rgokhman@bayareanewsgroup.com.