Officer Carlos Manfredi says several people were detained for questioning after the shooting yesterday.
The shooting triggered a chaotic scene as dozens of people ran screaming as officers carrying handguns rushed to the scene.
Manfredi says a 64-year-old man who was caught in the crossfire got shot in the arm. He's hospitalised in stable condition.
Four shots were heard in a witness video posted online. Manfredi says the argument had nothing to do with the gay pride event.