The footage - captured on a surveillance camera at a liquor store near the intersection of Riverside Drive and Whitsett Avenue - appears to show Los Angeles County Sheriff's detective Amber Joy Leist run across the street just as a vehicle that was traveling at a high rate of speed crosses the intersection.
Sheriff Alex Villanueva said Leist was stopped in her car around 11 a.m. when she saw a woman stumble as she tried to cross the street. Leist put her car in park and went to help the woman cross.
While returning to her vehicle, she was struck by the car, which had the green light, Villanueva said.
The detective was the 41-year-old mother of two sons, ages 17 and 20. She was transported to a nearby hospital where she was pronounced dead.
Residents say pedestrians and drivers need to stay on high alert at the busy intersection.
"It just seems like they're in another world now, they're focused on everything else but what they're doing, which is driving a deadly machine," one man said.
The driver involved in the collision stopped at the scene and was cooperating with investigators, authorities said.
"I have two boys and we sort of talked to them on the way to school this morning about just because you're on the crosswalk doesn't mean you're safe. You always have to look out for cars," one woman said.
Leist was a 12-year LASD veteran.
"It's one of those things that, when it did happen, what was she doing? She was helping somebody. That's a quintessential deputy sheriff," Villanueva said. "We are shocked and stunned by the sudden loss of a family member."
Dozens of law enforcement vehicles formed a procession, and a line of deputies saluted Leist as her flag-draped coffin was taken inside the morgue.
Leist had held various positions with the department, including working as a north county corrections officer, a deputy in Lancaster and a school resource officer. She had spent the last five years with the West Hollywood station where she was promoted to detective.
Today, @LASDHQ is grieving. We are shocked/stunned by the sudden loss of a family member. Amber Leist, a @WHDLASD detective, and 12 year veteran of LASD, was fatally struck by a vehicle in @LACity while assisting others. She was an outstanding detective who lead by example. pic.twitter.com/PcNIlAfTz8— Alex Villanueva (@LACoSheriff) January 13, 2020
A makeshift memorial - including flowers, a candle and picture of Leist - is growing outside the West Hollywood station.
The crash remains under investigation.