Developing news from Parkland, Florida, suggests heavy casualties in an active shooting situation at Marjory Stoneman Douglas High School.

Fox 10 News reports that at least one person has been killed in the mass casualty incident. Police have notified all area hospitals to expect injured students from the high school. Some students have reportedly been barricaded in classrooms as the shooter remains at large. Others inside the school are being escorted out with their hands in the air, per police protocol.

According to the latest information, the shooting first erupted in a classroom at the school and the teacher present who witnessed it will be meeting with investigators shortly for a debriefing.

Multiple unverified reports have indicated that at least 20 people and possibly as many as 50 have been injured.

The shooter reportedly remains at large and has not been publicly identified but authorities know who the suspect is.

This is a developing story. CrimeOnline will provide additional updates when more information is available.

[Feature image: Fox 10 News video screenshot]