Florida school shooting suspect Nikolas Cruz has been charged with 17 counts of premeditated murder.

The 19-year-old was questioned for hours by US federal authorities in relation to yesterday’s deadly massacre.

A charge sheet published online today confirmed his status as “pending trial”.

And as Cruz was taken to his cell, US President Donald Trump urged Americans to report “disturbed” people showing signs of “erratic behaviour” to the authorities.

Seventeen people were killed as gunfire erupted at Marjorie Stoneman Douglas High School, Parkland, just before classes ended on Wednesday afternoon.

The shooting is now ranked as the second deadliest act of gun violence on a US public school campus.

Cruz was arrested in a nearby community two miles from the school around an hour after the rampage.

CNN, citing law enforcement sources, said the gunman pulled the fire alarm and shot at staff and students before trying to blend in and leave among fleeing crowds.

Broward County Sheriff released a mugshot of deadly school rampage suspect Nikolas Cruz (Image: Broward County Sheriff)
Cruz has been charged with 17 counts of murder
Shaken students and teachers were escorted from the school yesterday (Image: Splash News)

The ‘very, very disturbing’ world of Nikolas Cruz: Florida suspect was ‘gun crazy outcast’ whose adoptive mum had just died

The teen later surrendered to police without a struggle, officials said.

He was armed with an AR-15-style rifle, multiple magazines of ammunition, a gas mask and smoke grenades.

Trump tweeted: “So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior.

“Neighbours and classmates knew he was a big problem. Must always report such instances to authorities, again and again.”

The shooting was the 18th in a US school this year, according to gun control group Everytown for Gun Safety.

A student who was in class at the time of the shooting said she “cannot unsee” the terror that unfolded before her.

Morgan Williams described on Twitter how her friends were killed as the gunman roamed through the school corridors.