Image copyright AP Image caption The surgery took 56 hours and involved a medical team of 60

On 16 June last year, Andy Sandness was wheeled into an operating theatre at the Mayo Clinic in Rochester, Minnesota, to undergo one of the rarest surgeries in the world.

Three weeks later, he would gaze in a mirror, unsure what he would see.

Reflected back at him was the face of another man: the nose, cheeks, mouth, lips, jaw, chin and even the teeth of his donor, Calen Ross.

What the two men had in common was that they had both, at the age of 21, turned a gun on themselves.

Unable to speak clearly after seeing his new face, Mr Sandness wrote a note for his doctors and family to read: "Far exceeded my expectations."

Media playback is unsupported on your device Media caption Andy Sandness gets a new face after trying to kill himself

Image copyright Eric M. Sheahan/Mayo Clinic/AP Image caption At the medical centre before his face transplant surgery

Mr Sandness, from Wyoming, was left with a face almost completely destroyed after his attempt on his life in 2006.

After extensive surgery, he still told people he had been in a hunting accident to explain his appearance.

Image copyright AP Image caption Mr Sandness says he instantly knew he had made a terrible mistake after his suicide attempt in 2006

Mr Ross, who lived in Minnesota, did not survive when he shot himself in early June 2016, leaving behind a pregnant and devastated widow, Lily.

She was committed to fulfilling her late husband's wish to be an organ donor but was uneasy about the prospect of another man taking his face.

"I didn't want to walk around and all of a sudden see Calen," she told the Associated Press.

But she gave her consent after being reassured that Mr Sandness had his own eyes and forehead and would not be identifiable as her husband.

Image copyright Eric M. Sheahan/Mayo Clinic/AP Image caption Dr Samir Mardani shows Andy pictures of his children moments before they go into surgery. The two say they are as close as brothers

Dr Samir Mardini, a specialist in facial reconstruction, spent more than 50 Saturdays over three years practising the surgery and transplanting the faces of cadaver heads.

They had estimated it would take years to find a matching donor, but five months after Mr Sandness was put on a donor waiting list - a match, in Mr Calen, was found.

The delicate and complex procedure included identifying nerve branches on the faces of both men and using electric currents to determine their function - smiling, or opening and closing the eyes, for example.

Image copyright Eric M. Sheahan/Mayo Clinic /AP Image caption It was the first face transplant surgery at the medical centre

Image copyright AP Image caption Andy Sandness plans to return to Wyoming and work as an electrician

This was crucial for Mr Sandness to be able to do those things with his new face.

Mr Sandness, now 31, and Lily have not met. But he has written her a letter, in which he spoke of her husband's favourite things.

"He's still going to continue to love hunting and fishing and dogs - through me," he wrote.