Castellanos is suspected of shooting two men in Garden Grove Saturday at about 4:50 p.m.
Costa Mesa resident Tyler Sanchez, 22, and Garden Grove resident Mauricio Marin, 24, were found suffering gunshot wounds at the intersection of Janet Street and Lampson Avenue.
Garden Grove officers arriving at the scene found a person wearing latex gloves attending to the victims, but police did not get a statement before the person departed. That person was urged to contact the Garden Grove Police Dept. at (714) 741-5800.
Sanchez was pronounced dead at UCI Medical Center. Marin remained hospitalized Tuesday in critical condition.
Police believe the shooting was gang-related.
The investigation led police to stop Ivan Castellanos in a vehicle, according to the department, at 2 p.m. Monday. He was arrested and booked at the Orange County Jail on a murder charge after being interviewed by detectives.
A weapon was not recovered, but police continued to search for one.
A photograph of the suspect was not released in anticipation of a photo lineup to be conducted with witnesses.
Anyone that can provide additional information was asked to contact the Garden Grove Police Department at (714) 741-5800. Investigators would like to talk with the person that rendered aid to the victims.