An orphaned 19-year-old with a troubled past and an AR-15 rifle has been charged with 17 counts of premeditated murder after being questioned for hours by police following the deadliest school shooting in the US in five years.
Fifteen wounded survivors were hospitalised as bodies were recovered from inside and around Marjory Stoneman Douglas High School in Florida.
Police say Nikolas Cruz, equipped with smoke grenades and multiple magazines of ammunition, opened fire with a semi-automatic weapon, killing 17 people and sending hundreds of students fleeing into the streets.
The 19-year-od was questioned by police for hours following the deadliest school shooting in the US in five years. Source: AAP
It was the nation's deadliest school shooting since 26 people died when a gunman attacked an elementary school in Newtown, Connecticut, more than five years ago.
CNN, citing law enforcement sources, said the gunman tried to blend in with students who were fleeing the school but was spotted and taken into custody without a fight about an hour after the shooting in a neighbourhood about two kilometres away.
He had multiple magazines of ammunition, authorities said.
FBI was warned
A Mississippi man said Thursday he alerted the FBI last year after spotting a chilling YouTube comment by a user with the same name as the suspect in the Florida school massacre.
The message - "I'm going to be a professional school shooter" - was posted under the name Nikolas Cruz.
The suspect in Wednesday's deadly assault at a high school in Parkland, Florida is 19-year-old Nikolas Cruz, who has been charged with 17 counts of premeditated murder.
"When I saw the comment come through my push notifications and YouTube studio, it caught my attention. So I screenshotted it so I can share it with the FBI," frequent YouTube user Ben Bennight told CNN.
The Federal Bureau of Investigation confirmed that in September 2017 it received information about the comment left on YouTube.
"The FBI conducted database reviews and other checks, but was unable to further identify the person who posted the comment," the agency said in a statement.
Bennight told BuzzFeed News that the morning after he reached the FBI, agents came to his office and asked if he had any more information about the person who left the comment.
"I didn't. They took a copy of the screenshot and that was the last I heard from them," he told BuzzFeed.
President Donald Trump earlier tweeted that there were "so many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior. Neighbors and classmates knew he was a big problem. Must always report such instances to authorities, again and again!"
A law enforcement official said late Thursday that the "FBI has begun an extensive review of how it handled the 2017 tip-off".
