So who is to determine who is “responsible” … the second amendment doesn’t concerned itself with “responsible”, just that all citizens have a right to own and bear arms.
You are responsible until you prove otherwise.
Your local tyrant. The National Reasonable-regulation Asses will be happy to substitute until you appoint one.
See http://www.nrawol.com links to keepandbeararms.com archive of NRA loving-gun control abuses that are as evil as Sarah Brady's and less honest. NRA recta osculate my fundament!