You seem to know that they knew something.
Owning guns is LEGAL.
Owning ammunition is LEGAL.
Owning body armor is LEGAL.
So, again, tell us what you know that the parents knew what this idiots was going to do. Show us proof. You made the statement.
I'm not sure why that matters at all. The Bills played the Chiefs relative early the past two seasons and then were elimimated by them in the playoffs both years.