Police spokesman Tyler Gamble says police were on their way to break up a big crowd when gunfire erupted at Bunny Friend Park.
He says ambulances took 10 people to hospitals, and police were told that others were taken by private vehicles.
Gamble says investigators don't know how serious the wounds are, or what started the shooting.
He says there were two groups at the park - people who had walked there in a neighborhood parade and people watching or participating in a video.
Gamble says the video was being made without a permit to use the park.