Around 2:50 p.m., Brentwood police and CHP officers were dispatched to the Highway 4 bypass north of Sand Creek Road after reports of a multi-vehicle crash. A Sig-alert was issued at 3:13 p.m.
Three people were transported to area hospitals and another was pronounced dead at the scene, according to police.
Officers determined that one vehicle sideswiped another vehicle before hitting a third vehicle head on.
Lanes began to open around 9:40 p.m. and by 10 p.m., all the lanes were clear, the CHP said.
The identity of the deceased is being withheld pending notification of the next of kin, police said.
The Brentwood Traffic Safety Unit is investigating the incident and asking anyone with information about the collision to call Officer Mike Homa at (925) 634-6911.