I was good with his actions until I read that he dragged (both) the teens bodies onto a tarp. Then, further lost me with his putting the gun under the girls chin and firing a second shot. Of course, making ANY comments was the wrong move as well.

If he'd have left the bodies where they fell, called the police once he felt the threat was neutralized - without KILLING if it could be prevented (which may or may not have been the eventual result of the first shot to the girl, but the second shot was clearly uncalled for), I'd stand with this guy and he probably wouldn't have been arrested. Sadly, he took it way to far.

Side note:
Mini-14 jammed: anyone who's ever owned or shot one knows how common that is.