Lori Rozsa Mark Berman The Washington Post

The armed school resource officer assigned to protect students at Marjory Stoneman Douglas High School took a defensive position outside the school and did not enter the building while the shooter was killing students and teachers inside with an AR-15 assault-style rifle, Broward County Sheriff Scott Israel said Thursday.

A heavily armed 19-year-old who had been expelled from a South Florida high school opened fire on campus shortly before classes let out Wednesday, killing 17 people while terrified students barricaded themselves inside classrooms, police said.

The armed school resource officer assigned to protect students at Marjory Stoneman Douglas High School took a defensive position outside the school and did not enter the building while the shooter was killing students and teachers inside with an AR-15 assault-style rifle, Broward County Sheriff Scott Israel said Thursday.

A heavily armed 19-year-old who had been expelled from a South Florida high school opened fire on campus shortly before classes let out Wednesday, killing 17 people while terrified students barricaded themselves inside classrooms, police said.