How should i take this from boss?

a few years ago my boss,me and co worker used to prank each other a lot.boss always said he was the best at pranks.but he started to see i was outwitting him.he got mad and said no more pranks.so i was ok with it.had not since.about a year ago we hired a new guy.he decided to play a prank on a co worker.well boss found out about prank but didn't know who did it.he asked me and i told him i didn't do it.told him i have not since he told me 2 years ago.well the new guy denied it.so my boss came up to me and other coworker and said if we didn't fess up he was going to start firing people.i told him again i didn't do it.finally after threatening new guy,well he finally fessed up.so boss came up to me and other worked and said we were off the hook.that's it!didn't even apologize!now im having 2nd thoughts about boss.me and other workers think he should apologize.after all he did threaten to fire us.accuse us of something we didn't do.even after we told him it was the new guy.what do you think?