Hm.
Must be people overreacting then. Could've been a truck backfiring.
Some people are saying it came from a group of people by a snack shop, celebrating? I am thinking it was a champagne bottle popping? But they said there one one initial POP sound, then some people starting running, then some time later, two more pops and then airline people behind their desks started running away. There was no security or police in sight when this happened.