Transcript for US Airways Bomb Scare: Was It an Ex-Girlfriend's Revenge?

Now, to the frightening bomb threat onboard a u.S. Airways flight on thursday. It was a passenger in handcuffs that was removed from the plane after authorities got a tip he might have explosives on him. It all turned out to be a false alarm. Sources tell us his ex-girlfriend might have been behind it all. Abc's pierre thomas joins us from reagan national airport in washington with the latest on this bizarre story. Pierre? Reporter: Good morning, elizabeth. S.W.A.T. Teams were all over that plane in a tense situation. But it was a hoax, apparently caused by a relationship gone bad. This morning, the fbi's investigating whether this scene was all just a vicious prank, possibly by a woman scorned. It all began at 7:30 a.M. Thursday, at philadelphia international airport. An ominous tip came in to police. There was a male passenger at the airport with explosives. Authorities quickly discovered the passenger, identified as christopher shell, was on u.S. Air flight 1267, which had already taken off for dallas. Fearing the man had snuck a bomb onboard, the plane was ordered back to philadelphia. Shell had no clue. He wrote on his facebook page. We spent an hour in the air before the plane had technical difficulties and had to turn back. Upon return, the plane was met by an army of fbi and philadelphia tactical teams. Five guys came on the plane loaded and guns drawn. You see the guy's rifle coming up alongside my face. About that time, he did an abrupt 90-degree turn and pointed it at the guy sitting next to me. Reporter: The drama continued as an exhaustive search was conducted. After all that, no bomb. Nothing. All indications are, that this was a hoax. And a pretty nasty trick was played on a passenger. Reporter: Sources tell abc news, police suspect the nasty trick may have been played by shell's ex-girlfriend and a male associate, timed for shell's birthday. He had just broke up with his girlfriend. He was going back to texas for his birthday. Reporter: The fbi is taking the hoax seriously. Since 2008, the justice department has charged 147 people in terrorist hoaxes. Look at the resources that were expending and the delays to the passengers. Obviously, there would be severe charges. Reporter: As for the victim, shell, there was concern about his background. So, police did a background check. Apparently, he had outstanding warrants. So, when he arrived in dallas, he was arrested by police.

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