In this frame grab from video provided by WPLG-TV, students from the Marjory Stoneman Douglas High School in Parkland, Florida, evacuate the school following a shooting. Picture: WPLG-TV via AP

Parkland, Florida - A shooting at a South Florida high school sent students rushing into the streets as SWAT team members swarmed in and locked down the building. Police were warning that the shooter was still at large even as ambulances converged on the scene and emergency workers appeared to be treating those possibly wounded.

Aerial television news footage showed police in olive fatigues, with weapons drawn, entering the Marjory Stoneman Douglas High School in Parkland. Then dozens of students could be seen frantically running and others quickly walking out. A police officer waved the students on, urging them to quickly evacuate the school.

Some students exited the building in single-file rows with hands raised overhead to show they carried no weapons. Others held onto other students as they made their way out past helmeted police in camouflage with weapons drawn.

Emergency medical personnel pulled stretchers from the backs of ambulances as police cars surrounded the parking lot. At least one person was seen being wheeled to the ambulance on a gurney. It wasn't immediately clear how many people were wounded.

AP