At least three students were killed and eight others were injured after a 15-year-old boy opened fire inside Oxford High School in a Detroit suburb. Stories about bravery and heroics among teachers and students are beginning to surface. One video, which you can watch below, shows students locked inside a classroom — when suddenly someone knocks on the door. “Sheriff’s office,” the voice said. “It’s safe to come out.” Someone inside the classroom wisely told the officer they were not willing to take that risk. The “officer” then told students, “Okay, well open the door and look at my badge,...