Police now say the shooting early Sunday morning happened at an illegal, underground party in a warehouse.
Investigators say the violence began with a dispute between two women at the party.
That's when someone brandished a handgun and a fight ensued, ultimately escalating into gunfire.
On Monday, officials identified two of three men who were fatally shot.
Randy Tyson, 25, and Daniel Dunbar, 27, both of Los Angeles, died at the scene, according to the Los Angeles County coroner's office.
3 dead, 4 hospitalized after shooting at warehouse party in Boyle Heights
Firefighters and paramedics were sent to a party where the shooting was reported in the 3300 block of East 14th Street about 12:30 a.m. Sunday, the Los Angeles Fire Department said.
Another man died at a hospital, according to the Los Angeles Police Department. Information on his identity was not immediately available.
One person was hospitalized in critical condition, two others were hospitalized in stable condition, and a fourth was treated and released, the LAPD said.
The shooting took place at a party that featured a performance by the Huntington Park rapper Money Sign Suede.
"Just wanna get on here real quick to send my condolences to what happened after this paid show yesterday," the rapper wrote in an Instagram post. "I pray for all the people who were injured and died last night."
No arrests have been announced.
Anyone with information on the case was urged to call (877) LAPD-247.
City News Service contributed to this report.