FORT LAUDERDALE, Fla. (AP) — When emergency calls began pouring in from parents and students during the Florida high school massacre, 911 operators at first tried to grasp the enormity of the emergency and then sought to calm the callers while gathering information to assist arriving law enforcement officers.

The Broward County Sheriff's Office on Thursday released audio of 10 of the 81 calls its 911 center received during the Feb. 14 shooting at Marjory Stoneman Douglas High School that left 17 dead and its aftermath. Calls came from students hiding in classrooms and parents who were getting...