Not mine - but a buddy of mine told me this one.
So, a buddy of mine and his wife and kids live in Santa Monica. They are a typical friendly couple and they lived below a nice elderly couple. No kids or grandkids, but very friendly and my buddy would go over and visit with them every once in a while. The kids became very friendly with them as well and become so familiar that they became surrogate grandparents to the kids.
So, they would always bring over cookies and they would have extra treats at Halloween. The whole deal...
Anyways, my buddy and his wife and kids go on a bike ride in Santa Monica one afternoon and they come home and their apartment is SWARMING with cops and FBI guys. I mean, everywhere.
My buddy has no idea what's going on. Goes up to one of the cops to see what's going on and to see if they can get back into their home and finds out that the sweet old man that lived upstairs was Whitey Bulger and his girlfriend.