I would like to know more about the son's training and access to the weapon(s). I love the outcome, but this could have easily turned out badly. I'm a HUGE gun rights advocate, but I'm also a HUGE gun safety advocate. Having a 15 and 12 year old in the house alone with your AR-15 service rifle...not such a good thing really. Unless perhaps the son was properly and extensively trained and the only one to have a key to the gun. A 12 year old girl should not be permitted casual access to weapons. 15 years old is even borderline.
Like I said, I am thrilled that this turned out as well as it did. But the "what if" scenarios bother me.