Broward County Fire Rescue is reporting that 20 people are injured, according to CNN affiliate WSVN.
The shooter is still at large, the sheriff’s office said on Twitter.
Aerial footage from WSVN showed a number of people lying on the ground outside the school, being treated for injuries and moved to ambulances.
Footage from the scene showed students streaming away from the school. Some ran, while others walked quickly in orderly lines with their hands on or above their heads.
Dozens of law enforcement vehicles are on site, including one tank, along with a team of heavily armed law enforcement officers.
Developing story – more to come