Its rare but very easy to do, there are so many variables and the story is so vague that I think the only people/person that will know exactly what happened were sitting next to him at the time.

My guess is the helicopter made a maneuver that prompted him to believe that it was landing. Usually when you first touch down its elbows and *******s anyway so you are pretty psyched for that moment.

But I don't want to guess on this Soldiers fate, stuff happens rip.