First Aid kit?
I keep a First Aid kit in the car all the time. I have a couple bandages (actually sanitary napkins) for 'bleeding wounds'. I was thinking primarily of being first on scene at a traffic accident, but that would also work for basic response to gun shot wounds as well.
If I shot someone in self-defense, I would render First Aid, depending on degree of wound and activity of the attacker, security of the site and anticipated response time of EMT and police. I would not just stand back and let anyone bleed out intentionally.