Odd that the US still allows children to serve on active duty I was surprised to see the age limit still at 17 when most of the developed world has moved on th UK for example is now 17 and 9 months at the point of sign on so you won’t finish basic before your 18th.Could serve. Also wasn't an AR-15. Is a replica which is typically tooled for a smaller calibre round.
Regardless the idea that he couldn’t legally vote or have a beer yet he is allowed to walk the streets with such a weapon unsupervised is pretty damning if the American system. Which ever way you cut it two men are dead and this young man’s life will never be the same again all because of a decision he took as a child.