We need to stop plastering every available surface with the name and face of everyone who commits a violent crime, encouraging the next one to go for the fame and attention, for a start. Then stop allowing repeat offenders to plea bargain their way out of jail just because they know some schmuck higher on the food chain has done something and are willing to testify, or they know someone on city council, or whatever the reason is. Commit a violent act, do the time.
Then we need to be willing to help, financially or emotionally, or whatever it takes to do it, people who clearly show signs of mental disorders. And keep track of who and where they are so if someone says "Oh yeah this guy is acting strange" then someone can step in to steer them on track again because they're already known to have problems beyond "had a shitty day."
As far as "high capacity magazines," the average crime involving a firearm involves less than four rounds fired, total. Unless of course the police are involved, then they'll shoot everyone around them and keep on firing until their guns are empty and people are laying bleeding in the street who were completely uninvolved...
Incidents like the shooting in Newtown are such a small minority of occurrences that they're hardly a blip on the radar. Most violent crime involving firearms are inner city black male on black male shootings involving a stolen gun, and a lot of them old five or six shot revolvers.
VERY FEW crimes, not just statistically but overall, are committed with "high" (or as someone not out to take rights away would refer to them as "regular" because they're the magazines the guns are designed around) capacity magazines, or what the media likes to call assault weapons. They're just the ones that get the most media attention. And the reporting system has been designed that way, to emphasize what helps the anti-gun political agenda the best.