At least 17 people have been killed in a shooting at a high school in Parkland, Florida, police say.
The suspect has been named as Nikolaus Cruz, 19, and is a former student at the school who had been expelled.
He reportedly pulled the fire alarm and caused chaos in the school before he started shooting, law enforcement officials told CBS News.
Students were forced to hide in classrooms as police scoured the building.
Broward County Sheriff Scott Israel told reporters that Cruz had used a rifle and had "countless magazines".
He said the shooting spree began outside the school where three people were killed. Cruz then entered the building and killed 12 people.
Two people later died after being taken to hospital.