Another tenant, high as fuck, thought that a firework was a candle. It doesn't help that he's not from the U.S. and had probably never before seen an unlit firework in his life.
I find it ironic that something would go bang on 9/11.
EDIT: IT WAS A FUCKING BOMB! WHY THE FUCK DID THIS DUDE HAVE A BOMB? WHAT THE FUCKING FUCK?!?!?!