The incident happened around 10:30 p.m. Saturday near Keystone Avenue and Venice Boulevard, on the first day of the Palms Community Festival, an event promoted by the Los Angeles Police Department.
Authorities say things escalated when a fight broke out between the victim and several other teens. One of them pulled out a knife and stabbed the victim multiple times, police added.
The boy, who has not been identified, died at the scene.
The suspect, who fled the scene and remains outstanding, was described as a man between 15 and 20 years old. Detectives say there were numerous witnesses to the fatal stabbing.
Authorities believe the incident is gang-related, but additional details were not available.
"Our entire community is shaken by the news of last night's horrific violence. My thoughts go out to the victim's family and friends, as they navigate this devastating loss," L.A. City Councilwoman Katy Yaroslavsky said in a statement. "My team and I are in regular communication with LAPD leadership, and have offered my office's full support as they investigate this heinous act and bring the individual responsible to justice."
The deadly attack happened despite a large police presence at the carnival. Those who turned out for carnival say it's tragic someone lost their life at the family-friendly community event.
"It's scary. I've lived here for the last two years and I've not felt scared at all, so just hearing about his news surprises me," said Josh Glodoveza of Culver City.