I've owned a 37mm Launcher (signaling device) and they're pretty safe and fun. I only used breaks (fireworks) and bird bombs but it's going to be interesting to hear what happened and I hope the guy is Ok. As in anything everyone should know that if you use ammo or weapons for anything else than what it's intended for then you put you or anyone else at risk
You could end up like this guy
*WARNING VERY GRAPHIC* - You've been warned
SAFETY
OUCH! Those last pics are pretty brutal...