From ABC News, regarding the VA Tech shooter:

Some news accounts have suggested that Cho had a history of antidepressant use, but senior federal officials tell ABC News that they can find no record of such medication in the government’s files. This does not completely rule out prescription drug use, including samples from a physician, drugs obtained through illegal Internet sources, or a gap in the federal database, but the sources say theirs is a reasonably complete search.

My question: The government has a database of people who have anti-depression medication, but they don’t have a database of anyone who buys a gun?