I hereby request that President Obama erect a large and prominently displayed sign in Washington D.C. with an electronic counter indicating how many days it's been since the United States last had a mass shooting.
If the country can go a certain amount of days without a mass shooting then they get rewarded. Examples:
* 30 days with no shooting = pizza party for literally everyone!
* 60 days with no shooting = $500 stimulus credit deposited to each and every taxpayer
* 90 days with no shooting = free entry to a Disney theme park
These are just ideas, of course. This will have the dual-effect of increasing awareness and incentivizing potential perps not to massacre innocents. Societal pressure to not ruin the pizza party for everyone else will also help.