Seventeen people have been killed and more than a dozen injured after a gunman opened fire at a Florida high school. Aerial footage showed students streaming out of the school with their hands in the air before dropping their backpacks into a large pile next to police and sitting on nearby grass. Sheriff Scott Israel of Broward County said the 19-year-old suspect - identified in media reports as Nikolaus Cruz - is in custody and that investigators are beginning to "dissect" what happened in the attack.