Many mass shootings involve legal guns [1]. These tragedies could be reduced by embedding short-range detection technology into various parts of the gun so that it would be easier to detect a firearm in public places such as schools.
These identification chips should be difficult to remove and only readable over a short range to protect privacy. Technology such as RFID tags can be used immediately, and are already used by some gun manufacturers. But research should be done to see if other technology is more appropriate or to improve existing technology for this application.
[1] http://www.washingtonpost.com/blogs/wonkblog/wp/2012/12/14/nine-facts-ab...