I've lost people to suicide with guns. In both cases, it was a single shot that killed them. Obviously, the gun didn't continue to fire without assistance. They could have driven a car into something, cut their wrists, hung themselves, taken a bottle full of pills... Yet we are not outlawing cars, knives, ropes, belts, medications, rocks, slingshots, spears, machetes, tomahawks...
People have been killing other people and themselves ever since Cain killed Abel...and there were no guns then.