I do have a bit of a problem with a 15 year old carrying arms without adult supervision. Just from a legal standpoint, anyone under 18 is not an adult and generally can’t be held legally responsible for their actions. The “charged as an adult” exceptions are in cases where there was a very serious crime, with obvious criminal intent, and usually a long juvenile rap sheet as well. “I forgot to make sure it wasn’t loaded” or “I forgot to consider the backstop” don’t get you charged as an adult (nor should they). The right can reasonably be curtailed for a minor or mentally deficient person who cannot be held to the accompanying responsibilities.
That's an easy one: EVERY gun is ALWAYS loaded.
First rule my kid was taught.