So we still know nothing about this guy. Here is my take.
He is the cell leader. Notice nothing was done by anyone to get out of Dodge until the FBI pictures were broadcast everywhere. They then needed to get the perps out of Dodge and not in one of their own vehicles, as the plan was told to the perps but they were about to become the daily sacrifice to protect the cell.
What I think was really going on was Mr. Coexist met them at the MIT location and someone called in a disturbance call from all the noise they were making to hastily get all the stuff in the car.
The cop shows up answering the call. They have to get rid of the cop so one of them distracts the cop by approaching the passenger side while another assassinated the cop after sneaking up on the drivers side while he was distracted with the first.
The problem is that the noise causes others to call in shots being fired but nobody knows what type of vehicle they got away in.
So now they are headed away until the car owner (Jack Ruby) magically shows up at the convenience store and tells his bullcrap story. What idiot spills the beans to a total stranger and then lets them go, especially when nobody knows what vehicle they are driving, Muslim or not? Being Muslim certainly does nothing to protect themselves in any other hell hole in the world, and it had nothing to do with this guy magically showing up who just happened to have a coexist bumper sticker on his car and leaving his GPS pingable cellphone behind.
If this Daily Mail account is to be believed, the guy was Chinese: