I like how all 3 replies ignored the part where I put in context "the moment police were getting close", as if to assume I was asking why fireworks were ignited at night in general. I saw the body cam footage, and the cops legitimately thought someone was shooting at them, because when they got close, they heard, what literally sounded like gunshots. Should they have just blind fired? Absolutely not, terrible training by those officers, but it's not hard to see why there would be some confusion.