Officials said guests of the wedding were leaving when a fight broke out between two people. Someone pulled out a gun and fired one shot, killing one person and injuring another.
Police are also investigating a crash scene on I-5 and Penrose Street, which is believed to be related to the shooting.
Authorities said a guest leaving the wedding lost control of his car and crashed into an embankment. Brothers Miguel Ochoa, 28, who is hospitalized due to injuries sustained during the crash, and 19-year-old Axel Chavez, who was also in the crash but was uninjured, were arrested.
"At this point, we're having some detectives completing the (wedding scene) and I have another scene that is awaiting photographs. And from those two scenes, we have several of the witnesses that are talking to us at the station right now. A witness is at the hospital talking to us," said Det. Pat Barron of the Los Angeles Police Department.
The victim was a 21-year-old man who was at the wedding. His sister-in-law and brother had just left the wedding before the shooting and said they don't know what happened.
Investigators are also looking at surveillance video they said was shot from the exterior of the building. They said the cameras may have captured a lot of what happened outside of the banquet hall.