If they thought that guy was him, they all need to take a forensic human identification course, specifically for living people.
I think they got a tip and didn't get a good look at him - and I wonder how many more men this will happen to. I am definitely questioning their tactics and give them low grades in being able to match BL to another living human. Eye sockets/eye shape are very different, just for starters. Eye brow shape is different too.
If the Marshals believe that BL is plucking his eyebrows (or could be shaving his facial hair), then they are going to find a big world of Brian look-alikes. Brian has a different ear shape (top part of the ear). They must also believe Brian is using a beard grooming tool, as the facial hair on the "suspect" is also different. The angle of the lower jaw is different - with BL having the more unusual shape (narrowing into a very different shape of chin - BL's chin is also statistically less common than the type of chin the other guy has). I usually start students with nose shape (the two men have different noses; BL's projects much further and has a wider base and nostril area is wider too: BL's nose is also less straight - has a bit of a bump). We really do have catalogues, language and stats for this in anthropology.
This man didn't have the tattoos. I'd like to think that Marshals wouldn't draw guns for this initial contact, until they had a chance to at least verify that. I guess that's not SOP for them, though. Scary.
The Marshals apparently thought this man was BL in part because his CC data traced back to NY. So that means they think that BL could have assumed another identity (and found a woman to stay with him in his room). What a wild ride this is going to be...
And if. that other gentleman is reading: your chin is much more pleasant to my eye than BL's, so no worries about losing the beard....