I'm not sure. It could have gone either way. I'm not sure what purpose the culprit would have in setting it, however. Pyro's body wasn't close enough to be caught on fire, and the explosion woke us all up, so that seems like an incredibly bad idea for the killer. The only thing I can think of for why they might have done that was to burn evidence... Could the fibers have been a part of something bigger that was burned, maybe?