Officers first responded to reports of a crash involving multiple vehicles on southbound Highway 280 north of Woodside Road at about 2:40 a.m., CHP Officer Art Montiel said.
A preliminary investigation revealed that the 25-year-old driver of a black Honda allowed his car to clip the rear of a Toyota SUV, causing the Toyota to lose control and strike the center divide, Montiel said.
Two people in the SUV suffered minor injuries.
Immediately after the crash, a witness in a Jeep pulled over on the right shoulder and got out of his vehicle, apparently to assist the crash victims, Montiel said.
As the man crossed the highway, he was struck by an oncoming Infiniti SUV and killed, according to the CHP.
Highway 280 was closed for around three hours, and the driver of the Honda, who was later identified as Charles Miranda, of Vallejo, was arrested by the CHP for suspected drunk driving.
Anyone who might have witnessed the incident should call the CHP at (650) 369-6261.