Judson Box said he was ‘so happy’ when a photo of his son was recovered, taken on September 11 2001

A father was able to have his pain eased ever so slightly after discovering a photo of his son not long before his death in 9/11.

The terrorist attack on September 11 2001 is a day that has been etched in history and will signify a heart wrenching moment for all Americans.

Judson Box is one of those Americans who was left with a lot of questions after the attack as his son, Gary, a firefighter disappeared on the day.

Gary, who was then 35 at the time had been working as a firefighter for five years when the attack happened and Gary didn’t speak to his father that day.

His death was surrounded in mystery for the family as his body was never recovered.

Nearly 3,000 people lost their lives in the terrorist attack on September 11, 2001 (Robert Giroux/Getty Images)

On September 11 eight years later, Gary’s sister, Christine, decided to visit the Tribute Center museum in New York and a worker asked if she was looking for someone in particular.

After mentioning her brother she was shown a picture, that was initially believed to be Gary, but it was in fact someone in his firefighting unit who had also died that day, Brian Bilche.

This lit a fire underneath Gary’s father who was determined to dig deeper in hopes of finding a similar picture of his own son.

This led him to search the photo archives of the National 9/11 Museum and the memorial’s website, but proved unsuccessful.

After a particularly exhausting evening searching he went to bed only to be woken by his wife the next morning who had managed to find a photo of Gary, running through the Brooklyn Battery Tunnel, on 9/11, in full gear, racing towards the towers.

The photo was taken a Danish businessman, Erik Troelson, who was eventually tracked down by Gary’s father for thanking him for giving this small bit of closure and likely the last photo of his son ever taken.

The businessman was able to capture the snap of Gary heading towards the towers (Erik Troelson)

“I was out of out control, emotionally,” Box told CNN. “Thanking God, being so happy that I had something to see.”

Reflecting on his conversations with Troelson, he added: “I think I said about 300 times thank you and God bless you, that’s all I could say.

“I think I told him I love you, and I don’t tell anybody that.”

Box also noted that he believes the museum is integral to ensuring people don’t forget the event and said he still felt the loss of his son on that day.