A high school student who survived the deadly Florida shooting on Valentine’s Day that left 17 people dead has slammed his teacher on social media, calling him an “opportunist” and “a coward,” after he allegedly wouldn’t unlock his classroom door and let students in, a report from the Sun-Sentinel said on Friday. Josh Gallagher, a junior at Marjory Stoneman Douglas High School in Parkland, Fla., shared his account on Twitter. He said he was in math class with his teacher Jim Gard when the fire alarm went off. Students began to evacuate, and while Gallagher was near the stairwell, he...