A man who released footage from the 9/11 attacks has spoken about what it was like to witness the atrocity.

On the morning of 11 September 2001, four planes were hijacked by the al-Qaeda terror group.

Two were flown into the Twin Towers in New York City, while another hit the Pentagon and a fourth – intended for either the White House or the US Capitol Building – was crashed into a field in Pennsylvania.

One person who witnessed the attacks in New York was Kei Sugimoto, who was 24 at the time.

On the morning of the attack, Kei woke up to move his car, in order to avoid a fine from New York City’s street cleaners.

But when he got outside, he saw crowds of people standing in the roads and staring in the direction of the World Trade Center.

Waking up just after the first plane hit the North Tower, Kei, now 46, originally thought there had been a fire in the building.

“I had just assumed it was an accident and there was a fire,” he recalled in an interview with LADbible, adding that he’d only gone to the roof of his apartment because he’d never witnessed a skyscraper on fire before.

This hypothesis would be shattered just over 15 minutes later when a second plane collided with the buildings, leaving no doubt in Kei’s mind that something more serious was taking place.

“I did see the second plane impact, and that’s when I thought, okay, for sure, this is not just an accident. This is intentional. It’s a terrorist attack,” he said.

It was at this point that he ran back to his apartment to grab his recording equipment and begin documenting history.

The attacks took place on 11 September 2001 (Spencer Platt/Getty Images)

As a small crowd began to gather on the roof, rumours spread among the building’s residents about further attacks on the Empire State Building or the Chrysler Building, while others worried about rumours about bridges and tunnels to the city being closed off.

There was also concern about the smoke coming from the building, and for good cause, as residents in the vicinity of the towers would later develop respiratory issues due to asbestos and other carcinogenic materials used in the construction of the towers.

Kei even recalled hearing about relatives of friends who lived in Chinatown dying of complications of ‘inhaling too much asbestos’.

After around an hour of being stood on the roof, Kei saw the towers collapse, something which he thought would never happen.

“When the towers collapsed, I thought it was unbelievable,” he said, adding that he thought authorities had been able to evacuate everyone inside.

“I assumed that people had been evacuated,” he continued. “It had been a pretty long time… So I had assumed everyone had already evacuated.”

Revisiting the footage nearly 23 years later, Kei admitted it was ‘shocking’ and ‘a little traumatising’ to see again.

However, he felt that – now he had the means to – the most important thing to do was to upload the video and ‘preserve history’.

Kei did reveal he’d had to re-upload a video due to a barrage of conspiracy theorists in the comments, however, the responses have been ‘largely positive’ with many commenters recalling their own experience from the day and thanking him for sharing the footage.

Kei has recalled the devastating events of the day (Jose Jimenez/Primera Hora/Getty Images)

“I did have second thoughts of uploading this to YouTube. But then again, I did think that I should from a historical archiving perspective,” he told LADbible.

“My grandparents lived through World War Two. And they told me a lot of stories before they died, maybe that has something to do with how I think that regardless of if it’s good news or bad news, it’s important to preserve history.”