Perhaps the least useful prism through which to view gun violence and its possible solutions is the rare and spectacular massacre. By all means, ban assault weapons. Most shooting deaths occur with handguns, though. Improve mental health services; most shootings are not done by crazy psycho killers, though. The predictive factors for a lot of gun violence are things like poverty, low rates of university education, lax gun laws in red state like Utah, and the like.
Of course, we also want to lessen the chance of these horrific mass killings, because they are horrible and frightening. That should be initiatives narrowly focused on prevention of this kind of event, but in the context of addressing gun violence in general. We could prevent all those lone-gunman-shoots-up-mall killings and still do nothing to address the other 50,000 gun homicides a year. Or we could make serious inroads on the more statistically significant problem, and still have the occasional outlier who is able to get the guns to carry out his plans.
Your chances of getting murdered in any given year in the US are .003%, or three one thousands of a percent. That's a rate of 3 per 100,000. That's unacceptably high, for several reasons.
*Other advanced countries have rate much, much lower than that. So it should be possible to lower the rate to a negligible level.
*Murder is a very bad way to die and affects younger people disproportionately, as do other somewhat preventable kinds of events like accidents and suicides.
*Homicide has a disproportionate effect on certain communities, where the rate is much, much higher than that 003.%.
I personally am not afraid of getting murdered, because for my age and race and general level of social interactions, it would be a much rarer than 003.% chance. If there are 100,000 living in a statistically average town, and 3 a year are murdered, it is not going to be me, most likely. Of course, men are more likely to kill and be killed than women, but still, I am not going to be too worried. Even if the chances were random, and three names were picked out of a hat to be killed each year (Shirley Jackson's "Lottery"), I would still probably die of old age. Say I had a life span of 80, so 240 names are pulled from the hat each year, out of 100,000. That's 24% of 1000, so 2.4% out of 10,000--so .24% is my chance of dying that way in 80 years. Unacceptably high? Yes, because we shouldn't have anyone put to death. I am against the death penalty too.
Whenever I start thinking anecdotally, based on watching the news and newsworthy events, I get a little bit stupider. Newsworthy events are much more likely to be rare and hence, well, newsworthy.