Amen bro. Finally some common sense.
Some of the posters suggest calling the cops or beating him up. What the hell for? A dumb Halloween costume?
I dressed as a commando this Halloween including a fake gun (camera attached to paper suppressor). Should I get blown away by the police just walking from dorm to dorm or get beaten up because I look like a terrorist?
How stupid.
What was suggested was that he be asked to leave the party.
Apparently you are neither a jew nor a friend of someone murdered by this type, nor related to anyone whose life is on the line.
This was despicable to any sane adult.