Ms Hall also says Mateen would always

Omar Mateen pictured when he was a freshman at high school in 2001. Former elementary school classmates have revealed he once threatened to go on a shooting spree at the school

Orlando gunman Omar Mateen threatened to bring a gun into his elementary school and kill everyone when he was just 10 years old, a former classmate has claimed.

Mateen, 29, was shot dead in a gunfight with police in the early hours of Sunday morning after opening fire inside the Pulse nightclub in Orlando, Florida, killing 49 people and injuring dozens more.

Now classmates who attended the same school as the shooter in Port Lucie have claimed that teachers often had to deal with his unruly behavior and threats of violence against other pupils.

The claims come just a day after classmates at his high school said that Mateen openly cheered on 9/11 as they watched in horror as two hijacked planes crashed into the World Trade Center in New York.

Lesley Hall, who was a 5th grade classmate of Mateen at Marisopa Elementary School in Florida told TMZ she recalls one occasion where he threatened to go on a shooting spree.

She explained that he told a group of children that he planned to bring a weapon into the school and open fire, killing everyone.

Ms Hall added that when students told teachers at the school about the threats, they were taken extremely seriously and Mateen was suspended for two weeks.

The former classmate also claimed she lived in constant fear of Mateen due to his relentless bullying of her, and even in middle school, he threw chair and spat at teachers.

The school district have so far refused to comment on the claims.

They come after reports that while Mateen was a sophomore in high school, attending a Spectrum Alternative School, a school for students with poor grades or behavioral issues, he cheered during the 9/11 attacks.

According to the Washington Post, Mateen's class was watching broadcast video of the first plane hitting one of the towers that morning when the second plane hit on live TV.

After the second plane hit, a former classmate recalls that Mateen 'stood up in class and...started jumping up-and-down cheering on the terrorist'.

Classmates say Mateen threatened to bring a gun and shoot everyone while attending Marisopa Elementary School in Port Lucie, Florida

'Mateen was smiling. It was almost like surreal how happy he was about what happened to us,' the student recalls.

The former student, who spoke anonymously to the Post for fear of his business clients learning that he attended an alternative school, said Mateen also claimed that Osama bin Laden was his uncle.

Another former classmate told the Post that Mateen started misbehaving after the two towers were hit, and that he was sent to the dean's office.

'I was sleeping in class and woke up to see people jumping off buildings, so I started swearing and they sent me up,' the former student said. 'But Omar was saying some really rude stuff. Stuff like, "That's what America deserves." That kind of thing. It wasn't right.'

Robert Zirkle, who was a freshman at Martin County High School at the time but who rode the same bus as the shooter, says that Mateen began taunting other students on the ride by making plane noises.

Mateen, 29, was shot dead in a gunfight with police in the early hours of Sunday morning after opening fire inside the Pulse nightclub in Orlando, Florida, killing 49 people and injuring dozens more

Zirkle says he believes Mateen was suspended or expelled from his school shortly after 9/11.

On the day of 9/11 itself, another student recalls seeing Mateen's father pick him up from school and slap him across the face in public.

'They had to escort him out of the school,' Zirkle said. 'Other kids were trying to fight him. A couple days after, they had to take him off the bus.'

'A few of my friends wanted to fight him because he kept doing it and saying crazy things,' he added. 'It's weird. He was totally cool before 9/11, and then something changed.'

Mateen's lasting fascination with terrorists was obvious when he called 911 from inside the Pulse nightclub on Sunday.

One classmate recalls that Mateen was suspended or expelled from the school after his behavior on 9/11. Above, the alternative school in Stuart, Florida that Mateen attended at the time of the attacks

On the day of 9/11 itself, another student recalls seeing Mateen's father pick him up from school and slap him across the face in public

FBI Director James Comey said in a statement on Monday that the shooter was involved in precisely three calls to a 911 dispatcher at approximately 2:30am.

Comey said: 'He (Mateen) called and hung up. He called again and spoke with the dispatcher and hung up.

'And the dispatcher called him back and they spoke briefly.

'During the calls he said he was doing this for the leader of ISIS, who he named, and pledged loyalty to.

'But he also appeared to claim solidarity with the perpetrators of the Boston Marathon bombings and solidarity with the Florida man who died as a suicideb bomber in Syria for Al-Nusra Front - a group in conflict with the so-called Islamic State.