One solution to the gun problem is to require registered gun owners to join the National Guard. Such a requirement would serve the general population in many ways, the least of which would be the creation of a large civilian force properly trained in disaster response for events such as Hurricane Sandy or Katrina
The National Guard goes through the same basic training as the military, so it could also be argued that this requirement could result in a large pool of the population prepared to prevent or stop an active mass shooting.
A further benefit would be the adoption of the National Guard selection process - applicants with mental issues would be identified and screened from ownership before they actually were permitted to possess a gun.