Is he fixed? I would hope/assume he already is, but sometimes males get really aggressive for no apparent reason if they have not been fixed. And we are now entering "kitten season" so he might hear all those females looking for love outside.

I also am not too sure of the "jail" because they often associate their crate with stressful things like the vet, and you already admitted he hates the vet. If he hid under the bed, I'd have left him cool off under there on his own. Shut the door to the bedroom if you wanted to be safe away from him.

I'd try to get some Feliway and see if that helps him. Its supposed to help with cats acting very stressed.

Also, have you changed anythig in the home lately? He might be reacting to something different that is no big deal to you, but it is to him. New carpet? Re-arranged furniture? New work schedule? Cat are hghly sensitive to change.