Police suspect the driver could have been drunk when she hit the people, including a number of children, outside St James Catholic church, Redondo Beach, last night.
Witness Marc Zonno told KNBC: "The crosswalk was full, and the light was red. Someone ran a red light and... bodies started flying...It was pretty horrible."
The people were leaving a Christmas pageant at the church when the incident happened.
A woman is being charged with manslaughter.
Police have only identified two victims - 81-year-old Mary Anne Wilson and 87-year-old Saeko Matsumura.
The church stayed open through the night to let people pray for the dead and injured.