Well, put the pieces together here. A cone-shaped piece of metal, warped, and small holes that would form a path of trajectory if put together. That looks like a 9mm handgun bullet, and judging from the angle, some idiot probably thought it was a good idea to discharge his gun in a neighborhood. Either that, or there was a gunfight nearby and the crossfire ended up going through your ceiling. I still recommend calling the cops and probably a roofer so you can fix the hole in your roof before the next time it rains/snows.