The Dodge minivan, which was carrying six people, ran into the truck at about 8:45 p.m. on Worthley Drive at Grant Avenue, CHP Officer Peter Van Eckhardt said.
The driver was immediately killed, and three occupants were trapped inside the van, Van Eckhardt said.
The trapped passengers were extricated, but one later died, he said. Two ambulances were called for the other passengers.
The crash happened in an industrial part of San Lorenzo, Van Eckhardt said. It's unclear whether the truck was stopped when it was hit or if it had been parked after the workday.
There had been no mention of a driver as of about 10:30 p.m.