Let's say that one person accidentally stumbles upon one of those insane "zombie walks". You know -- where people put on studio-grade makeup so that they really look like zombies in every way. And even smell like them. And let's say that this person shoots a person thus disguised and kills him. Is the fact that the person thought that the moron dressed up as a zombie really was a zombie a defense against murder charges?
A prompt answer would be very, very appreciated.