Good point. The judge was being a bit hyperbolic, but excessive use of alcohol is a factor in many shootings. Teenage drinking, regardless of legal drinking age is a problem as well.
So some say reducing the legal drinking age is a solution? I say, salude!
Some cultures define age of majority as thirteen years old. Most U.S. states it is later. Unfortunately, children mature at different rates and there will always be laggards.
The most effective solution would be derived from a cultural-level change.
Where I live most of drunk people that cause accidents are +40, the younger generation does in general not drink if they drive. We understood the problem and thought our children not to drink and drive. And with success. Our children can buy alcohol from the age of 16 I think.