I think this murdering bastard was a probe, and I expect the evil demons in the sleeper cell who gave him the ok to do what he did now have on video tape, complete with aerial views, a pretty good idea of what happens during an evacuation of that terminal, where the crowd goes, how the security responds.
The next hit at the airport will take advantage of this information, and not be so small scale.
He was no 'free-lancer".