Luis Amela, 41, was fatally shot in the parking lot of Sky Burgers in the 1800 block of East Palmdale Boulevard on March 31.
Investigators say Amela was shot four times when he tried to stop someone from stealing his bike outside the restaurant.
A 17-year-old boy and a 17-year-old girl were arrested on suspicion of involvement or assistance with the killing Wednesday at approximately 3 p.m., deputies said. The gunman, however, remains at large.
The suspects were booked at the Palmdale Sheriff's Station and appeared in Sylmar Juvenile Court Thursday.
No further details were immediately released. Anyone with information on this incident was urged to contact the Los Angeles County Sheriff's Department's Homicide Bureau at (323) 890-5500.