After a gunman killed 49 people in June at a gay nightclub in Orlando, Fla., Anne Verrill, a prominent Maine restaurateur, swung through a range of familiar emotions: frustration, anger, helplessness. She reflected, too, on her typical response to the nation’s litany of gun massacres. “We write Facebook posts, we copy and paste, and we talk about it with people who basically agree with us,” Ms. Verrill, 38, said the other day. “We’ve never really done anything outside the box with regard to gun control.”