The Los Angeles County Sheriff's Department initially said the victims were shot at three separate locations, but later clarified the injuries stemmed from one incident.
Some sort of argument broke out near Whittier Boulevard and Leonard Avenue around 9:40 p.m. Investigators say the suspect pulled out a handgun and started shooting.
Two men and two uninvolved bystanders, only identified as a woman and juvenile male, were hit by the gunfire.
Those bystanders later showed up at different locations, which created some initial confusion for law enforcement.
All four victims were taken to the hospital with non-life threatening injuries.
Details about the suspect, or what else led up to the shooting, were not available.