In their "defence" 50k split across the multiple people present is just not enough - 500k would have been more likely to be accepted, I think

Charging someone with bribery must be a first in the history of the RTP

I was returning today on a packed UA flight BRU-EWR in coach row 26. As we were all getting off, the usual scramble occurred with everyone getting their bags down from the overhead. A gentleman in front of me assisted a woman with her bag in an overhead that had her bag and a large briefcase (everything else was gone inside). He then took out the briefcase and proceeded to exit. A guy a couple of people behind me yelled "hey, that's my bag", the guy in front of me said "sorry, thought it was mine" and the bag was passed back to the owner. I'm still right in back of him, and saw him walk off the plane without taking anything from any of the overheads, which by now were all empty. The guy was dressed normally with a sports jacket and appeared to be in his mid 30's (not that it means anything), and had a very heavy accent. I heard him speaking to the woman he assisted. Should I have said something to the FA's or security? I lost sight of him on the way to passport control.

Yes, you should tell your flight attendants right way. That's important. You should have tell her right way. They will take care of it. You have to catch a thieves. They will have to talk with him. They will arrest him.