Officers say a woman in her 40s rear-ended a semi-truck just before 3 am Saturday on Highway 99 near Mission Avenue.
When she pulled over and got out on the roadside to check for damage to her car, another oncoming semi-truck sideswiped her car, which then hit and killed her.
Another woman was inside the victim's car and she is being treated for her injuries at the hospital.
The cause of this deadly crash is still under investigation.