Thousands of students and parents poured into the school in Florida where a mass shooting nearly two weeks ago claimed 17 lives.

The students accompanied by their parents on Sunday returned to the Marjory Stoneman Douglas High School in Parkland, Florida, where the February 14 massacre took place.

The students walked past police cruisers and memorial flowers to gather the backpacks and books they had left behind as they fled, the New York Times reported.

They hugged their classmates, teachers and friends they hadn't seen since the massacre.

"It actually felt good to be in the building," said 17-year-old student Briana Valli. "We're all going through this together."

Another student, Ryan Senatore, said: "It makes you feel kind of empty inside."

"Walking back in where 17 lives passed -- it's a disgusting feeling. It's never going to be the same. Never," said the 15-year-old.

Teachers and the rest of the staff were expected to return to work on Monday and Tuesday. The students will be back for classes from Wednesday.

Some students said that they dreaded returning and that wandering around the school again felt "surreal". The school was now a place filled with grief counsellors, comfort dogs and posters of solidarity.

The three-storey building, where most of the shooting occurred, remained fenced off and closed. It will not reopen for classes, said the daily.

School officials, parents and students have called for it to be demolished, with a memorial built in its place.

Meanwhile, new details emerged about the 19-year-old school shooter Nikolas Cruz that revealed a disturbing photo about his home life.

Cruz watched his adoptive father die of a heart attack in 2004 when he was just five years old. Years later, the teen reportedly tried to kill himself by guzzling gasoline just days before turning 18, according to Sun-Sentinel daily.

He was bullied relentlessly by his younger brother through his teens, reports said.

Cruz was diagnosed with developmental disorders when he was three years old and was described as "lost", "lonely" and "violent" by people who knew him.

He was also reported to the state for posting a video of himself cutting his arms on the mobile app Snapchat.

While he was a student at the Stoneman Douglas school, he was once seen in 2017 clutching a dead bird to his crotch during reading class, Cruz's former classmate told the Sun Sentinel.

He is currently booked into Broward County jail after confessing to the shooting.