The woman, identified as Maria Casteneda-Nunez of Lawndale, was crossing the street when she was hit by the truck. After she fell, a Metro bus ran over her.
The truck driver kept going at first but then came back and surrendered to police.
Police said the driver of the pickup truck was detained for questioning and released, pending the outcome of an investigation.
The bus that struck Casteneda-Nunez has yet to be identified. Authorities said Metro officials were cooperating in the probe.
City News Service contributed to this report.