The woman died at the scene and the other was taken to a hospital, but an update on her condition is not available at this time, according to police.
The police department's investigations bureau responded to the scene and officers are collecting evidence.
Anyone with information is asked to call the Antioch Police Department at (925)778-2441 or text-a-tip to 274637 (CRIMES
No other details about the case were released by police.
ABC7 News contributed to this story.