WARNING: Video contains violent content not suitable for all viewers. Discretion is advised. In a video shared on social media on Thursday, a passenger can be seen running up behind a flight attendant standing in the aisle of the plane, before appearing to punch them in the back of the head. Other passengers on the flight from Cabo, Mexico to Los Angeles, Calif. seemed to cry out, with one shouting, "Oh my God!" It was not immediately clear what led up to the incident. According to reports, the passenger who struck the flight attendant was detained by the FBI upon landing.