Insurance is what enables this accountability. The state crime victims' compensation fund, whenever a crime involving guns is committed or a gun mishap occurs. The more victims, the bigger the payout. The insurers will also pay the fund for other claims, such as when a minor commits suicide by gun or accidentally kills a playmate with Daddy's pistol. This will reduce such mishaps.
Insurance is very effective in getting people to adopt safe practices in return for lower premiums.
When a crime involving a gun occurs, the firm who insured it pays the claim. Like other insurance, firearm insurance will be from a private firm or association, not the government. Any financially-sound group, such as the NRA, can follow state insurance commission rules and create a firearms insurance firm. No mass or government registrations. Except for defining the rules, no government involvement at all.