The couple who provided a home to the Florida school shooting suspect before the Valentine's Day massacre has given evidence before a grand jury considering formal charges in the case.

US president Donald Trump has defied many of his supporters in gun lobbying group the National Rifle Association (NRA) by saying assault rifles should be kept out of the hands of anyone under 21.

Some 100 students from Marjory Stoneman Douglas High School will travel 400 miles to Florida's capital on Tuesday to urge politicians to act to prevent a repeat of the massacre that killed 17 students and teachers last week.

Florida's child welfare agency investigated the suspect in a school shooting that killed 17 people after he cut himself in a video, but found him to be stable, according to state records.

US president Donald Trump came face-to-face with hospitalised victims from the horrific school shooting in Florida and offered thanks to the doctors and nurses who helped the wounded, declaring "the job they've done is incredible".

The FBI has admitted it was told last month that the Florida school suspect could be plotting an attack, but agents failed to investigate.

The names of the victims of the shooting massacre at the Marjory Stoneman Douglas High School in Parkland, Florida, on Wednesday have begun to emerge.

At least 1,000 people have attended a candlelight vigil for the 17 victims of a school shooting in Florida.

An orphaned 19-year-old with a troubled past and an AR-15 rifle was charged with 17 counts of premeditated murder on Thursday morning after being questioned for hours by state and US federal authorities following the deadliest school shooting in the country in five years.

Donald Trump has been labelled a "shit" on Twitter by a user who is believed to be a student at the Florida school where 17 students were shot dead.

The suspect in a deadly rampage at a Florida high school is a troubled teenager who posted disturbing material on social media before the shooting spree that killed at least 17 people, according to police.