I also want to know where the gun came from. How did it get into the hands of a minor? If it was one of the parents then they are responsible too and should do time as well.
I see your point on that and if it was found the parents were grossly negligent then hell yes, at least 2nd degree manslaughter.
By age 15, 16 and 17 most kids know if their parent has a gun and if it's not locked up, a bad kid can rummage through mom and dads room and find it even if it were in a safe place. These punks were old enough to know better.
My opinion won't be popular on this matter, but if you can afford $400-$600 for a gun, then you can afford $600-$1000 for a gun safe. Or at least a small good secure Sentry Fire safe for about $250 for hand guns and bolt it down in your closet. All together, hand guns, shot guns and rifles, I've got about 20. All but one are locked in my gun safe. Under the bed, in a closet, blah blah blah just isn't safe enough for any household. Crooks may get in my house and take TVs, Tools and computers, but they won't have time to get in the gun safe in 90% of most cases. JMO, if you have guns you need a safe. And I don't mean some tin box with a lock on it, or a nice wooden curio cabinet with frosted glass of a deer scene on it and a little piss ass lock.
I trust my kids whole heartedly and to this day and they were raised with guns and been shooting since big enough to hold one. My kids still don't have the combo of my gun safe I've had for 15 years and they are now 17 and 25 years old. My wife, now ex, didn't have the gun safe combo. I don't even know it. But, I know where to get where it's stashed in print without any reference so noone would know what it is if they seen it. And passworded file on my computer and hdd back ups. In the event I croak off, when the kids go through my crap, they'll find that safe combo and that's when they can have it.