Trip Reports - all chained up

I was on a Northwest flight routed through MSP last weekend. I walked to the bathroom and there was this guy at the door (not in uniform) who gave me a really weird look. I was thinking okay this is kind of awkward. Then I walked into the bathroom and there was this other guy with what I thought was the longest chain I had ever seen hanging off of someone’s pants. He began to walk towards the sink and I took a second look and noticed that he was handcuffed and his legs were shackled, I walked way around him. It completely took me off guard. I‘ve seen prisoners transported on planes in movies but this was the first time I’ve seen it in real life. Has anyone else ever had an experience like this?

Ah, it was you. Sorry if I scared you...

Yes, I've seen them on flights from Hawaii to the mainland on UA. I forget all the requirements (and they may be specific to UA), but I remember they must board first and exit last, sit in the back rows, each has one or two armed marshalls with him, and prior to using the restroom it must be checked by a marshall.