Ralph Demicco, a gun shop owner in Hooksett, N.H., was shocked in 2009 when three of his customers bought handguns and committed suicide over five days in separate shootings. He encountered firsthand the stark, barely noticed fact that more than 60 percent of the nation’s 30,000-plus gun deaths each year are acts of suicide, not accidents or homicidal attacks. In New Hampshire, where the suicide rate is 31 percent higher than the national average, over 85 percent of firearm deaths are suicides.

The dealer reviewed the shop’s surveillance tapes. There were no giveaway signs of the troubles driving these customers to shoot themselves. “It’s just an ugly, ugly thing,” Mr. Demicco later told researchers for Harvard University’s School of Public Health. “I decided I must become involved.”

And he did, joining a pioneering effort that avoided the typical gun-control debate between two entrenched factions. Instead, he focused strictly on the suicide problem in collaboration with public health and mental health professionals, other firearm dealers and gun rights advocates. They worked on a program to educate gun owners about research that shows they face a higher risk of suicide than other people — not because they are more suicidally inclined, but because guns are so lethally efficient when used, and are often too easily at hand.