Away with permissive parenting. People with out-of-control kids need to keep them away from their guns — or face the consequences. And, unlike the fools who parented the murderous Harris and Kleybold at Columbine High, they need to be aware of what weapons their kids are bringing in from the outside — or face the consequences.
If the young man made it to age 17 without having committed a crime, then I think there is little evidence of "permissive parenting".
Imagine the message it sends to the peers of the 17-year-old to have people blaming the parents for the actions of a person who is within months of being an adult for practically all purposes?