In a life or death situation? I don't know for sure, but I've read that anybody that knows how to handle a rifle starts popping away. And I imagine a Marine Corps Major as down to earth as Greg, even if he is a flyboy, knows how to handle a weapon.
See, the troops loved him. You could tell. He was one of them. That was the difference. I don't know if he got the pulitzer for that reporting job. He probably didn't but he should have. He rode into hell with those guys.
All Marine Corps aviators do a short tour with a ground unit before going to their operational squadrons, so they know what the mud Marine's world is like.