Police believe they know who the gunman is, saying he was wearing a hoodie and has red hair.
Authorities said the incident occurred around 2:30 p.m. at Marjory Stoneman Douglas High School on Wednesday, February 14, 2018.
Police said an active shooter is to still at large.
"Avoid the area of Stoneman Douglas HS. #BSO is currently working a developing incident regarding a report of active shooter," Broward County Sheriff Office wrote on twitter.
According to Buzzfeed, one male student, who was not identified, said that he was on the campus at the time of the shooting, adding that other students near him heard an alarm go off and initially they thought the school was staging some sort drill. Then they heard gun shots.
"We heard pops, the student said, and from the other side of the school we see the whole school running out," he said.
A statement released by the school district said the shooting happened closed to dismissal time - when students heard what sounded like gunfire, the school was placed on lockdown.
Police believe they know who the gunman is and have described him as a student and member of the JROTC program. Authorities said he was wearing a hoodie and has red hair.