But murder is not the kind of gun violence that kills the most Americans.

In 2010, the last year for which complete numbers are available, the number of gun deaths by suicide in the United States outnumbered homicides 19,392 to 11,078. If you add up all American gun deaths that year, including accidents, 3 out of 5 people who died from gunshot wounds took their own lives. Those figures are not an anomaly: With just a few exceptions, the majority of gun deaths in the United States have been self-inflicted every year since at least 1920. This is a startling fact, and one that forces us to realize that, no matter what we may believe about the Second Amendment, the debate over how to reduce the death toll from guns is, to a great extent, a debate about suicide prevention.

“A lot of people, when they think about guns and violence—suicide is just kind of off the radar screen,” said Daniel Webster, the director of the Center for Gun Policy and Research at Johns Hopkins University. Webster added: “People think about the gun problem as something that someone else is going to do to them.”

With President Obama’s call for tighter gun laws working its way through Washington, and a national debate over gun rights underway, public health researchers around the country are making the argument that the issue of suicide should be a much larger part of the discussion. To reduce gun deaths as they really happen, they say, will mean not just fighting crime or keeping firearms out of the hands of potential killers, but trying to minimize the number of people who have access to guns during their darkest hours.

At the heart of this argument is the idea that the vast majority of people who have committed suicide by shooting themselves would have stayed alive if they had not been easily able to pick up a gun. This can be a difficult premise to process. First, it goes against a common intuition about suicide: that someone who wants to end his or her life will find a way to do it by any means necessary. Second, it presents a destabilizing challenge to both sides of the gun control debate, which have traditionally drawn their emotional power from people’s fear of murder.

But if the reckoning our country has been engaged in since the Newtown tragedy is driven primarily by a desire to save lives, experts say, it’s time to recognize that in the majority of cases, the people doing the shooting are also the ones who are dying.

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For Cathy Barber , a researcher at the Harvard School of Public Health, suicide became a priority in 1999, while she was engaged in a dark, emotionally draining task related to a research project on violent death. The project centered on a massive database tracking the circumstances under which people are killed, and Barber was reading through thumbnail summaries of violent deaths—thousands of them—that had taken place around the country.

At the time, her work focused on homicide and domestic abuse. But as she looked at the stories she and her team had collected, she realized that when it came to gun deaths, she was reading mostly about people who had taken their own lives. “The stories were so filled with despair and misery, but the seeds of hope were in them, too,” Barber said. “I kept thinking, ‘So many of these seem preventable.’”

Today Barber directs a suicide-prevention campaign at Harvard called Means Matter, intended to promote the notion that how people commit suicide is just as important as why—and that making it harder for suicidal people to get access to guns is a relatively simple way to save their lives.