Focusing too much attention on gun laws while failing to deal with important underlying problems has proved to leave us with more problems rather than fewer.  When Reagan was shot gun control was the first response.  At the same time people were released from mental institutions and funding for community mental health was cut.
Mass killing are frequently associated with suicide. Suicide attempts and other forms of self-destructive cause much suffering and some deaths.  Both community mental health and education can help prevent more serious outcomes.
When Columbine happened I hoped that educational practices would be changed instead of a focus on gun control.
Things like mass killings and suicides have a certain contagious aspect.  Amok behavior was reported in an area of the South Pacific in the 1800s that seemed to be a part of that culture. If we care about real improvement the conversation must go beyond gun control.