17 persons killed in a Florida school shooting.

Seventeen people including children and adults have been  killed when a gunman entered the high school on Wednesday afternoon and launched an attack.

Twelve people were found dead inside the school, two were killed outside the building, one in the street, and two died later in hospital from their injuries.

The suspect has been named by police as 19-year-old Nikolas Cruz. He was arrested at the scene and is being questioned by investigators.

Florida Gov. Rick Scott ordered government flags flown at half-staff through Monday in honor of victims of the shooting at Marjory Stoneman Douglas High School, a public school of some 3,000 students outside Boca Raton.