If negligent behavior caused the shooting, then filing criminal charges on the shooter and then civil action would be appropriate...if negligence was involved.
Except you're in the hospital for a few months, the assailant (if caught) is in jail earning $0.00. Likely we're not talking about a hedge fund manager as the perp to start with so good luck getting your cab fare to the hospital in the judgment much less your medical bills, pain, suffering, etc... If you're really unlucky, you're the spouse/parent of someone who goes through all of that then passes away.
Hence the need to have something built into the system to reimburse the wounded and killed and their families.