The CHP said a Toyota and a red pickup truck were involved in an accident first. Investigators believe Hylla got out of her car, possibly to get help, when the Sheriff's patrol car collided into her Toyota.
"She may have been out of her vehicle, and once the secondary collision occurred, that may have propelled her onto the other side of the freeway," said CHP Sgt. Adrian Torres. Authorities said Hylla's body was launched over the center divider and into the southbound lanes.
Two male deputies and an elderly couple were taken to local hospitals for minor to moderate injuries.
The Toyota was so badly damaged, emergency personnel couldn't tell if there were other victims inside. The Sheriff's vehicle had front-end damage.
The deputies involved were on duty at the time of the accident. It was previously reported that they were off-duty.
The 405 North was closed for several hours while authorities investigated the accident, and traffic was diverted off. The backup stretched for several miles during the morning commute. Two left southbound lanes were also closed until the coroner cleared the scene. Lanes were reopened at about 9 a.m.
The CHP said people should remain in their cars if they are involved in an accident on the freeway.