At least 17 people are dead after a 19-year-old man opened fire at a high school campus in Parkland, Florida, police have said.
The suspect has been named as Nikolas Cruz, a former student at the school who had been expelled.
As the attack unfolded students were forced to hide as police swooped in on the building.
It is the deadliest school shooting since 26 people were killed at Connecticut school Sandy Hook in 2012.
It is the sixth school shooting incident in 2018 that has either wounded or killed students.
Broward County Sheriff Scott Israel told reporters Mr Cruz killed three people outside the school, before entering the building and killing another 12.
Two people later died after being taken to hospital.
“It’s catastrophic. There really are no words,” Sheriff Israel tweeted later.