Has happened before unfortunately. I remember in 1990 at KPHX, when the Phoenix city drunk tank used to be located just outside the fence on the southwest side of the airfield.....where Swift Air is now......an Alaska Airlines 727 was taking off at night on 26L. A guy from the drunk tank had wandered off and onto the airport and the runway and was stumbling down the runway. 727 crew sees him in their landing lights at around 100 knots and tries to steer right to avoid him, but smacks him with the left main landing gear. Takeoff aborted, and the jet taxied back in with what was left of the drunk guy.