The transcript of that dad's interview with law enforcement last year gives some insight into his thought process and what was going on.
The son was clearly having a lot of mental health issues, with blame being directed at bullying at school.
Dad says the son wanted to change schools to get away from it (which is apparently what happened as he then moved to a school in a different county where this shooting then occurred).
The dad although not agreeing it happened for sure, seemed to believe plausible that his son had made threats to take violent action at the school, saying to the effect 'I hope he didn't/doesn't do something like that because then I'd have to take his access to the guns away'.
It is pretty clear that at least at that time, the dad wasn't securing the guns at home. And thus likewise a reasonable guess that the gun used in this school shooting was also not notably secured by the dad. It was the son's gun with easy access to it.
Was clear the dad felt gun ownership was a good way to improve the son's present mental health problems, talking about how it was opportunities to bond with him, hunt deer together, get out of the house and away from the video games.
When you have young man like that who apparently is an outsider at school and perhaps being verbally, even physically bullied, perhaps having a gun can help self-confidence and even give a feeling of power...but the danger here is that can lead to an obsession to the power to retaliate with violence.
And that is where the crucial flaw and poor decision making from the father IMO is apparent. Yes, hunting with your son, your son participating in gun ownership...all okay but not if the son is not only in a poor mental state but is showing clear red flags for potential violence.
You don't give a gun to a child who has made threats about shooting up his school... threats that even got you drug into an interview with law enforcement.
You want to bond with your son and get them out of the house away from the video games. Go fishing or hiking instead. Or, if guns just has to be your main go-to thing, then go hunting together but for damn sure you don't just let the kid have access to a gun all to himself. Not while there is still a lot of work to do on the mental health side.
One of the girls in the math class said that kid rarely showed up for class. He was frequently skipping school, clearly the problems from the previous school had followed him to the new one, there is no way the dad didn't know his son wasn't in a good way.
I don't agree with the 2nd degree murder charge on the dad, but I do think just like the Michigan case that involuntary manslaughter is appropriate charge at this time. And then let all the facts come out in a trial and let a jury decide.