Forbes article on that explains in detail why, unlike the vague others:Old tactic, one I think they could only do in this case because the parents begged him not to do it hours before he did it. Ie they knew and didn't call it in.
They'll prolly still not get convicted though.
Michigan School Shooting Suspect’s Parents Charged With Involuntary Manslaughter
The Oakland County prosecutor indicated her office was considering charges against Ethan Crumbley’s parents during a press conference earlier this week.
www.forbes.com