[El Gato]

while carrying an assault rifle.....

Possibly broken into two backpack size pieces, or just as likely they are using one of the single shot handguns chambered for .223. That would at least help to explain the lack of follow up shots on the two he didn't kill, too slow. Although truth be told, not THAT slow, unless he/they are using one of those where the breach has to be screwed off and on after each shot. Possible, as at least one of that style can be chambered for .223.

[AntiGuv]

The only reason I pointed out the weapon - however it's being carried in and out - is to make the case that whoever this is apparently hasn't drawn any attention (looks like he 'fits' in). If he had drawn notice, then they would near certainly have found the weapon wherever it was being hidden. It's very unlikely in my view that the sniper looks Middle Eastern because it almost goes without saying that in the present mood they would not escape notice (esp. carrying a backpack..) Aside from that, I fully agree with the rest that he's almost certainly disassembling the weapon for carry purposes.