Stop contributing to the NRA. Contact your state representative and advocate for magazine capacity restrictions. Ask for better background checks for purchasing firearms. Ask for training to be required before purchasing firearms. That training could also act as a psych eval. If you don't like those come up with "something" yourself.
Your reply was almost perfect. When the pendulum swings too far the other way, it will be because responsible gun owners like yourself did nothing to contribute to a solution.
I expect your reply to be something like, "but, but, but how is that going to STOP these killings. The bad guys will still (get guns, use bombs, use trucks, use shotguns, use knives/axes/pointy sticks) "