Doesn't really matter since he would have passed the security screen anyway as he wasn't carrying anything.
As for suing the airline...that's an interesting question, eagl. The regime for international travel by air is the Warsaw Convention (as amended) in which the airline is automatically liable for any accident which occurs during the course of carriage (I'm abbreviating here for brevity)....question is whether this guy was shot during the course of carriage..most of the case law says that it begins at checkin and you are still 'in the course of carriage' until you have your luggage and leave. Somehow I don't think there will be a court action about this one, but this won't be an 'accident' so automatic liability won't kick in, although if there is a claim you can bet your bottom dollar it will be brought in Texas even if the passenger had nothing to do with the place becase that's where you get the highest damages, the maddest judges and juries and they have something against UK insurers or reinsurance market which are the people who will ultimately pay.
it will be an interesting case if brought...watch this space!