No less than 17 individuals have been murdered in a shooting at a secondary school in Parkland, Florida, police say.

The suspect has been named as Nikolas Cruz, 19, and is a previous understudy at the school who had been ousted.

He purportedly pulled the fire alert and caused bedlam in the school under the steady gaze of he began shooting, law authorization authorities disclosed to CBS News.

Understudies were compelled to cover up in classrooms as police scoured the building.

Broward County Sheriff Scott Israel told journalists that Cruz had utilized a rifle and had "endless magazines".

He said the shooting binge started outside the school where three individuals were slaughtered. Cruz at that point entered the building and executed 12 individuals.

Two individuals later passed on subsequent to being taken to healing facility.

Prior on Wednesday, the nearby government funded school area tweeted: "Today, near Marjory Stoneman Douglas High School's expulsion, understudies and staff heard what seemed like gunfire.

"The school promptly went on lockdown however is presently rejecting understudies."

Police were clearing understudies from the school "one working at any given moment", the school said.