Authorities arrested 19-year-old Eudiel Lopez around 5:45 p.m. Monday and booked him for murder.
Police say there was a confrontation involving a group of young men just after noon on Monday outside a market in the 9100 block of Painter Avenue. The victim, identified as Michael Soto, was shot during the confrontation.
The teen was transported to Whittier Presbyterian Hospital, where he was later pronounced dead. According to one witness, Soto was shot in the head.
Authorities say deputies tracked down Lopez in the 9000 block of Painter Avenue. A handgun believed to be the murder weapon was also recovered.
Whittier City School District officials believe Soto was a former student, although he was not currently enrolled at any of their campuses.
The suspect is homeless but has ties to the Whittier area. Sheriff's officials said the shooting appeared to be gang related.
Anyone with information about this incident should contact the L.A. County Sheriff's Department's Homicide Bureau at (323) 890-5500.