The crash was reported just after midnight at Gypsum Canyon Road, according to the California Highway Patrol's traffic log.
A person got out of their vehicle when they were hit and killed by another car, but additional details were not available.
Most WB lanes of 91 Freeway shut down after person struck, killed in Yorba Linda area
Several hours after the deadly incident, all westbound lanes except for the FasTrak lanes were shut down, backing up traffic all the way to the 15 Freeway in Corona.
After snarling the morning commute, all lanes were reopened by 7:20 a.m.