Suppose an angel came to you and offered an altruistic choice. A) You could end all mass shootings in America for 10 years, or B) reduce car accident fatalities by 10% for 1 year. What decision does your heart make? What choice does your head make?
Your heart might say to go with A. I think it was Stalin who said, "The death of one man is a tragedy, the death of millions is a statistic." Society is absorbed in the tragedy of every school shooting, most people don't even know the car accident fatality rate has been falling for years. They don't spend their limited attention on such statistics, but a moving story? We'll debate the implications on Facebook for weeks.
Use your head and you'll realize that by picking A, you've killed over 2,000 people. NOW use your heart to decide whether that's a good and moral choice.
The fallacy is in thinking that you have to choose between your head and your heart. Simply use your head and then use your heart. Don't ask your heart head questions and don't ask your head heart questions.
So what does our hypothetical story about the angel have to do with real life? When you assess mass shootings in proper proportion is seems dubious to base on it federal policy that effects 300 million people. The blip that is mass shootings cannot be what guides our policy decisions. Moreover, attention is a finite resource. We do ourselves no favors by hyper focusing on something that is quantitatively negligible.