Do you think the owner of the gun used in school shootings should be charge with a crime for not properly locking up the weapon?
No. The murderer is the only one responsible for the murder. Unless the owner of the firearm knew the murderer's plans and consented to them explicitly, they have no culpability in the matter.
I said no because the question seems a little bit obscure. Are we talking about charging the owners because someone had their gun, or proving, with evidence, that there was negligence?
If it can be proven that parents or other persons left the weapon or weapons out unattended, loaded and unlocked then yes, they should be punished. Owning a firearm is a great responsibility.
If you can't prove you are worthy of this responsibility, then you should not own a weapon.
Pretty sure in the incident you are referring to the weapons were indeed properly secured. The kid defeated the safeguards to acquire them.
Assuming he was indeed negligent, then yes.
Naw, leave it loaded on kitchen counter
Yes, if that is the situation.