I would start by measuring the magnitude of mass shootings as a problem. How does it compare to other issues such as preventable diseases, regular crime, terrorism? I searched for data, and found out that in the past 30 years, 543 people have been killed in 70 mass shootings. That’s an average of 18 deaths per year. For comparison, three times as many die from lightning strikes.
The New Republic article linked in the previous paragraph states “I can’t say exactly why mass shootings have become such a menace over the past few years, and especially in 2012.” Given the low numbers, it’s likely that it is just a random fluctuation without statistical significance.
To put things in perspective again, half a million Americans die every year from tobacco use. Two hundred thousand die from medical errors. Those numbers are large enough that it’s possible to track changes with statistical significance, and evaluate the effect of public policy. There must be a fair amount of low-hanging fruit. For example, it’s feasible that a 100% tax on the price of cigarettes would save thousands of lives ever year. Why is this not attempted? Probably because the special interest group that controls tobacco sales is powerful enough to stop it.
For mass killings, the numbers are already so low that the logical question would be: is it worth doing anything to try to reduce even more the chance of mass killings? What could be the undesired side effects of implementing policies to that effect? For example, let’s say that someone came up with a vaccine that guaranteed that a child who received would never be a mass killer. However, one child in 100,000 dies from an adverse reaction to the vaccine. Clearly the vaccine itself would cause more deaths than mass killings, so it’s a net negative if we are trying to minimize unnecessary deaths.