With the specific intent of tracking down the mentally ill with high risk factors for spree or impulse murders.
All background checks would be minimally invasive, and any other cases of criminal wrongdoing would be overlooked. Unless an individual draws up "red flags" for a specific psychological profile, no further investigation will occur.
This phenomenon has existed for a while but is becoming increasingly widespread in the United States. While greater population density may be a contributing factor, there is a chance that spree killers represent a shift in the serial killer paradigm.
http://en.wikipedia.org/wiki/List_of_rampage_killers#Domestic_violence
Just me or have there been a lot of these lately? We'd like to help you help America, but this is pretty distracting. Jobs.