Today marks 18 years since the world's most famous terror attack, which changed the city of New York forever.
As the Twin Towers were being engulfed in flames on the morning of 11 September 2001, nearly 3000 people were desperately trying to escape the inferno before the World Trade Centre inevitably collapsed.
Among those that joined the rescue effort were almost 300 dogs. One of these canine heroes was Labrador Roselle. The fearless guide dog saved her owner and 30 other people, calmly leading them to safety down 80 floors, navigating them through fire, smoke and debris.
Michael Hingson, a sales manager for Fortune 500 company Quantum, had first met his guide dog in 1999, and she was sat under his desk, just like every other day, when the disaster struck.
In an interview with the Sunday Express, Michael told about the moment he knew something was wrong.
"I heard a tremendous boom, and the building started to shudder violently, before slowly tipping, leaning over 20 feet," he said.
"Those inside became convinced they were on the verge of death. Tearfully, colleagues said goodbye to each other. I was sure I was going to die."
Although they didn't know it at the time, the building had just been hit by American Airlines Flight 11, which is said to have been hijacked by Al Qaeda terrorist Mohammad Atta and four others. After the initial impact, the building slowly, somehow, righted itself.
And then the repercussions of the impact began, with debris beginning to fall down around his colleagues.
Michael said: "I had always paid attention to fire drills and I knew to avoid the elevators, take the stairs and not to panic.
"While everything was happening, the explosion, the burning debris, the people in the conference room screaming, Roselle sat next to me as calm as ever.
"She didn't sense any danger in the smoke and flames, everything happening around us.
"If she had sensed danger she would have acted differently, but she didn't. Roselle and I were a team and I trusted her."
They headed towards the door, surrounded by unsure people with no idea what to do. At this point, the 3000 degree heat from the explosion above was making its way down the elevator shaft.
As Roselle led Michael down the stairs, more people began to follow.
"We started to walk down and I noticed a strong smell, a little like kerosene," Michael continued. "Suddenly I realised what it was. As a salesman I'd flown all over the world and I'd smelled it on runways. It was the smell of jet fuel. Then I thought- what if a plane had hit the building?"
As the group, led by the hero Labrador, descended down the building, the kerosene in the air became so strong it started to burn their eyes as they passed wounded people with horrific injuries.
"I suddenly thought - what if the lights go out? There was no real panic yet. New Yorkers are tough. But that could change if the stairwell was plunged into darkness.
"The thought hit me that I could be a guide. So I called out to everyone not to worry, that Roselle and I would lead the way. Some people laughed, but the mood was definitely lightened."
After an hour, they finally reached the lobby. Michael tried to call his wife Karen, but couldn't. He would later find out that this was because of the sheer amount of people trying to get in touch with their loved ones.
Suddenly, a police officer started shouting at them to evacuate as the building was collapsing. Michael recalls that it only took around 10 seconds for it to fall to the ground. Michael picked up Roselle and began to run with her, quickly realising that everybody was now running for their lives.
"I heard the sound of glass breaking, of metal twisting, and terrified screams. I will never forget the sound as long as I live.
"Then we were engulfed by a monstrous cloud of sand and gravel. It filled my throat and lungs and I was drowning, trying to breathe. But we kept running, and Roselle kept guiding me perfectly. She didn't stop once. Roselle and I are a team, and I was not about to let her go."
Hingson was one of the lucky survivors and he puts it all down to Roselle's guidance. He went on to leave his career in sales to work for Guide Dogs for the Blind - the organisation that had paired him up with Roselle.
Roselle retired from guiding in 2007 after medication she had for a long term illness began to damage her kidneys. She lived with Hingson until 2011, when she was diagnosed with a stomach ulcer and passed away.
But the heroic legacy of Roselle lives on. In her memory, Roselle's Dream Foundation was set up to continue to help visually impaired people. She was posthumously named American Hero Dog of the Year 2011 by American Humane and even has a book written about her.
Thunder Dog: The True Story of a Blind Man, His Guide Dog, and the Triumph of Trust is available now.