President Obama turned a campaign event in Fort Myers, Fla., into a moment of silence, calling on participants to pray for the victims of a Colorado shooting. “This morning, we woke up to news of a tragedy that reminds us of all the ways we are united as one American family,” Obama said of the mass shooting during a midnight showing of “The Dark Knight Rises,” the latest Batman movie, at a theater complex in Aurora, Colo. Twelve people died and dozens more were injured. If anything, an incident such as the one in Aurora shows that “life is very…