The incident occurred at the station located on Vermont Avenue and Santa Monica Boulevard around 9:20 a.m. Metro spokesperson Jose Ubaldo said a male passenger traveling to Union Station was stabbed in the throat.
The victim was transported to L.A. County-USC Medical Center in grave condition. The L.A. County Sheriff's said the victim was pronounced dead at 6:36 p.m.
The suspect was described as a black male between 18 to 21 years old. The suspect ran away without witnesses getting a good look at him, but the train and station are equipped with closed-circuit surveillance cameras.
The knife used in the attack was not recovered.
Ubaldo said trains were initially bypassing the station, causing 15 to 20 minute delays for other passengers. The station was reopened for service around 11:30 a.m.
Anyone with information or who may have witnessed the stabbing was urged to contact the Los Angeles County Sheriff's Department at (323) 563-5000.