For anyone still reading this, I just wanted to share that one of my buddies in the pop-up camper called me again today to say, "Thanks." He had left his rifle in his truck and for a second, when he peeked out the door and saw how close the guy was to his truck, he worried the guy was shooting his gun. He said he felt completely helpless without a gun and was really thankful that I handled the situation as I did. He pointed out that he had some training in the military that involved possible interactions with civilians (presumably armed), but that he had never actually had to confront someone.
Anyone that thinks I was wrong to have a gun pointed in the direction of the unknown, reckless perp hasn't had their ears blown out by a rifle shot in the absolute darkness. The fear was real and I wasn't going to wait to verify that, yep, there's a hole in my daughter or one of my friends before I recover from all the disadvantages I was at.
And yea, next time I'll wait the guy out while I'm lying on the frozen ground in my long johns...
The only thing I would do differently is have a gun ready to go and a bright/blinding headlamp/gun-mounted light so I didn't have to ask the perp to turn on a light so I could see what he was doing or how many friends he had with him.