We need to redefine mental-illness. Violent crimes are not normal behaviour of healthy people.

I have a hard time believing that "people without any mental-health problems at all" committ so much violent crime. More a question of redefining mental-health.
According to the National Journal "Researchers estimate that if mental illness could be eliminated as a factor in violent crime, the overall rate would be reduced by only 4 percent. That means 96 percent of violent crimes—defined by the FBI as murders, robberies, rapes, and aggravated assaults—are committed by people without any mental-health problems at all. Solutions that focus on reducing crimes by the mentally ill will make only a small dent in the nation’s rate of gun-related murders, ranging from mass killings to shootings that claim a single victim."

http://www.nationaljournal.com/magazine/why-improving-mental-health-would-do-little-to-end-gun-violence-20130124?mrefid=skybox