This doesn't come out of nowhere. They "gave their son a gun and ignored warning signs of violence."
Right and it sounds like they or, at least the wife, still doesn't understand that they did something wrong.
Is it a crime to give a gun to a minor? I suspect not because America. The article says that they were convicted of involuntary manslaughter; does that feel appropriate? I can certainly see it that way, but it certainly looks to me like these people are being singled out because the US is not able to systematically address gun violence.
Not just "warning signs". She was texting the kid "don't do it" while he was on his way to shoot up the school. she knew it was about to happen and didn't notify the school or police.