The exact cause of the disturbance was unclear, but several people seemed to have serious injuries and were being treated by paramedics.
The LAPD said it appeared at least nine people had been injured - and six of them may have been stabbed. Some of the injuries may also have occurred as the crowd fled in panic.
Earlier in the day, hundreds of people had gathered peacefully at the store where the rapper had been slain Sunday afternoon. Fans were gathering to remember him.
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Later Monday evening, a disturbance suddenly broke out in the crowd and people began fleeing from the store.
The exact cause was not confirmed, but various unconfirmed reports ranged from gunshots to a stabbing to fireworks. Other reports indicated at least one person was struck by a car.
The LAPD later tweeted that there was not a shooting at the site: "Our men and women are on scene and making every effort to protect everyone in attendance at the Nipsey Hussle vigil. Reports of shots fired at the vigil do not appear to be accurate. We do have injured in the chaos and are attempting to restore order."
"We understand the community is mourning and we feel your loss. We are asking for everyone to follow the officers' directions and disperse from the immediate area."
LAPD officers began forming skirmish lines and keeping people away from the scene.
Look at all of the shoes people lost during the stampede... an area where candles were lit near the @NipseyHussle memorial area was also trampled. Police still trying to clear the area. @ABC7 pic.twitter.com/c4dmnE2K7V— Veronica Miracle (@ABC7Veronica) April 2, 2019
DEVELOPING: This story will be updated.