MINNEAPOLIS — Juanita Jensen grew up in a gun family. She doesn’t hunt, but believes in the sport and is used to having guns around. And as the parents of five children, Juanita and her husband were careful to follow all the rules for firearm safety: Keep the guns separate from the bullets. Lock up everything. Enroll their teen boys in gun-safety classes so they could learn to hunt responsibly. But despite all of their precautions, they realized just how tough it is to keep guns away from someone who shouldn’t have one.