Tread lightly, Americans: Nearly 9% of people in the United States have outbursts of anger, break or smash things, or get into physical fights -- and have access to a firearm, a new study says. What's more, 1.5% of people who have these anger issues carry their guns outside the home. The findings, published Wednesday in the journal Behavioral Sciences and the Law, suggest that measures to reduce gun injuries and deaths should focus less on diagnosed mental illness and more on a history of violent behavior.