Consider this, if the father were asked "would he do anything differently?", my guess is, he would strongly regret his judgement with the gun. It's not a handgun, or a rifle. I doubt any one of us would agree to bring a high powered machine gun into our home and give a key to a 19-year-old.
I wouldn't even give my car to a 19-year-old without a lot of proof that he was stable, healthy, trustworthy, etc.
This dad was wrong, even though he meant well.