Two Los Angeles County Sheriff's Department deputies were shot in the head in an ambush at the Metro station in Compton Saturday evening.
Surveillance video showed the two officers sitting in their patrol car when a man in dark clothing approached the vehicle and opened fire at close range before running off.
Both officers received multiple gunshot wounds and were hospitalized in critical condition.
Sheriff Alex Villanueva called the shooting "a cowardly act."
"The two deputies were doing their job, minding their own business, watching out for the safety of the people on the train," he said. "To see somebody just walk up and start shooting on them. It pisses me off. It dismays me at the same time. There's no pretty way to say it."
One of the officers was identified as a 31-yea-old woman with a six-year-old son. The other was identified as a 24-year-old man.
US President Donald Trump retweeted the video of the shooting, writing "Animals that must be hit hard!"