Florida school shooting: First victim of massacre named as Chris Hixon

The first victim of the Florida high school massacre has been identified as the school's athletic director.

Chris Hixon, 49, was killed when troubled former student Nikolas Cruz opened fire at Marjory Stoneman Douglas High School on Wednesday (local time).

"Chris is such a great guy," his friend Dan Jacob told local news site Sun-Sentinel.

"Chris is probably the nicest guy I have ever met. He would give you the shirt off his back. He does so much. That is terrible that it would happen to anybody. It is so senseless.

"I am crushed... I am totally crushed."

Seventeen people died and dozens of others are now receiving treatment for gunshot wounds after Cruz's mass shooting.

He had been expelled from the school for disciplinary reasons, according to media reports, but he returned to carry out the massacre.

Traumatic footage from one of the classrooms that escaped unscathed shows the sheer terror of the moment as Cruz unleashed shot after shot in the corridor just metres away. A number of students can be heard screaming and swearing as the gunfire gets closer.

Another sporting leader was badly wounded in the attack. Coach Aaron Feis, also employed as a security guard at Marjory Stoneman Douglas High School in Parkland, was shot and wounded after jumping in front of the teenagers to protect them.

Mr Feis survived, but is now battling for his life in hospital.