So I think he's mid 20's, Middle eastern or Mediterranean heritage, lives somewhere on the east coast (Atlanta or points north).
Grudge with this specific company. Imagines himself as some sort of movie antihero assassin (silenced weapon, Monopoly money, rounds with words written on them). Into fashion. Meticulous with his appearance. Disciplined. Intelligent.
I don't think his beef was with this particular victim, rather, I think it's with what he symbolized. I say that because if he did have it out for this guy, he'd just hit him in his home state. It would be much easier, and much less risky.
This is an ego thing for him, which is why he chose committing this crime in that place, and in that way. He wanted it to be caught on camera. It's practical as well, as what better way to get his message across?
I think he's graduated college, perhaps currently in some postgrad program. He has access to money, as his clothing, backpack, and the trip itself were quite expensive.
None of this really gets us anywhere, but I just wanted to put this in writing for when these questions are answered.