The Sacramento County coroner's office identified him as 36-year-old Spencer West Myers.
The incident began at about 4:55 a.m. when a Fairfield woman lost control of her 2004 Toyota Camry while driving east in the No. 2 lane west of Dixon Avenue, CHP Sgt. Phil Grant said.
The Toyota overturned and landed on its roof in the fast lane, Grant said.
Myers pulled over near the center divider east of the crash scene to help, Grant said.
A short time later, both Myers and the overturned Camry were struck by a 2002 Dodge Stratus driven by a Fairfield man, Grant said. The woman in the Camry was ejected from her car.
She and Myers were both taken to the University of California at Davis Medical Center, where Myers died at 6:11 a.m., according to the coroner's office. The woman is expected to survive, Grant said.
The driver of the Dodge was not injured, and was not cited for any violations, Grant said.
Grant said the CHP does not want to discourage people from stopping to help at accident scenes, but wants to remind them to be aware of their surroundings.
The deaths of good Samaritans "happen all too often," Grant said.
The crash is still under investigation.
The accident blocked lanes, and the CHP issued a Sig-alert at 5:05 a.m. All of the eastbound lanes were briefly shut down at Midway Road at about 5:20 a.m. to allow a medical helicopter to land on the highway.
All lanes were cleared shortly before 7 a.m.
