yes, the gimpy arm kinda matches how suspect 2 is almost always holding his arm at 90 degree angle.
suspect 2’s hand is larger. Me thinks he was wearing a high definition silicone prosthetic hand which are quite easy to get these days.
http://www.aestheticprosthetics.com/clients/hands/h4.html
Is the arm really gimp or is he just holding it that way to not drop the backpack? It’s only slung over one shoulder. Try walking naturally with a backpack slung over one shoulder. You can’t. I’m sure he really didn’t want to drop that backpack.