I never heard Michael had a gun on him. Where did you see that?

Anyway, they knew they were potentially dunzo. Michael put all his jewelry in a bag and told his wife if he wasn't back by 9, there was trouble.

I imagine they were resigned to the fact that if their number was up, it was up.

It is interesting that they chose to beat them to death rather than just shoot them. I can only imagine it was because Aiuppa and Cerone were enraged they were basically going away for the rest of their lives and blamed Tony for bringing down so much heat. At least that is the way it has been explained to me before. Makes sense.