Cellphone video has surfaced of the mass shooting from inside Marjory Stoneman Douglas High in Parkland, Florida.
The video, tweeted by CBS Evening News, shows student crouched down as shots ring out.
Another video has surfaced of a SWAT team entering a classroom of scared children.
Broward County Sheriff Scott Israel said at least 14 people were injured in addition to the 17 who were killed when Nikolaus Cruz, a 19-year-old former student opened fire, notes NBC News.
Israel said Cruz had been expelled from the school for disciplinary reasons.
Cruz allegedly fired a AR-15-style semiautomatic rifle outside and inside the school; he was apprehended about an hour later.