The suspect, 28-year-old Narada Brooks, was arrested Friday night at an apartment building in La Habra. He is charged with three counts of murder and is being held without bail.
Brooks' connection to the victims is unclear, but investigators say it appears he acted alone.
"Just through the detectives' follow-up, it appears that he is the only one wanted for the shooting," said LAPD Officer Sarah Faden, adding that the investigation remains active.
The shooting happened around 5:30 a.m. Friday in an apartment in 1600 block of West 205th Street in Harbor Gateway. Three men were killed, and a man was found with a gunshot wound to his leg a few blocks away near Western Avenue and Del Amo Boulevard. Authorities tracked him down by a blood trail. He is in the hospital in fair condition.
It is unclear what led to the shooting.