NOTE: For simplicity's sake, I'm only talking about the U.S.
Mass shootings are clearly given more attention, relative to other problems, than the harm they cause. They are certainly not one of the leading causes of preventable death, and they are only a tiny share of all gun violence. Is it worse for a number of people to die in one shooting than it is for the same number to die in separate shootings? No, but the former will get way way more attention. You would save far more lives if you were able to decrease the number of deaths caused by cigarettes by 1% than if you ended all mass shootings. The amount of attention the media gives to a problem does not represent how big it is.
We can expect bringing more societal attention to a problem to cause a reduction in that problem, on average. But there are good reasons to suspect mass killings are an exception to that rule. Many experts believe that the media attention brought to these killings is one of the main incentives for future mass killers. And you can't just blame the media for that: our demand is what drives their coverage.
To do my small part in reducing mass shootings, I choose not to click on news articles about them, which gives the media less incentive to make such a huge deal about them.