Darryl Kitto, 47, was on an outing with some friends near the Rakaia Gorge when he fell to his death.

Darryl Kitto, the last surviving member of his family, was with his carers when he slipped and fell 40 metres to his death while having his photo taken.

The 47-year-old Christchurch man was under the care of community mental health service Emerge Aotearoa when he died on Sunday at Rakaia Gorge, in Mid Canterbury.

Kitto had an intellectual disability and was unable to live independently.

WESTPAC RESCUE HELICOPTER/SUPPLIED Emergency services attend to the fatal incident.

It was understood the woman taking his picture was one of his carers.

The group had already taken one photo when, looking to get another photo from a different angle, Kitto slipped on a grass embankment and fell from the cliff.

Senior Sergeant Pete Stills said Kitto died shortly after his fall.

"He wanted to get a photo with the gorge in the background, he got too close to the cliff edge and he appears to have slipped."

Kitto fell about 40 metres, then hit a tree.

"He was unresponsive and appears to have died at the scene," Stills said.

Senior Constable Andy Grant said the people with Kitto at the time were "traumatised".

Kitto was the last surviving member of his immediate family, and had little contact with his extended family.

Originally from Dunedin, Kitto was moved to Christchurch in his youth to be cared for by a disabilities service.

His closest surviving relative, aunt Noeline Devlin, said the family had limited contact with Kitto.

She knew he had formed a close attachment to his father, Dick, before he died last year.

"That's their whole family gone now," she said.

"We never really heard from [Kitto]. The only time I really saw him was at his dad's funeral."

Kitto's parents split when he was a child, but reunited 35 years later.

His mother, Cheryl, died of cancer in 2008, and his younger brother, Gavin, died of a heart attack in 2003.

Following his father's death, Kitto expressed a desire to leave Christchurch and return to Dunedin, but was unable to do so.

"He got very close to his dad in his later years. Him and his carer would make trips down to Dunedin to see him.

"In his mind, he thought he would be able to come back to Dunedin, and it was still going to be like it was when he left. He just had the wrong idea."

In a statement, Emerge Aotearoa chief executive Barbara Disley said the "tragic" accident was under investigation.

"At this stage our focus is on supporting the people who were close to him and the people who were with him at the time."

She said it would be inappropriate to make further comment.