Two hikers who were seriously injured in the Mournes had to be evacuated to hospital by helicopters on Saturday evening.
Rescuers were called out about 4.30pm after two of a group of four men climbing down the east end of Slieve Bearnagh lost their footing and fell.
The first man suffered head and back injuries and the second was hurt while trying to assist his friend.
Neville Watson, who co-ordinated the Mourne Mountain Rescue Team (MMRT), said the first man had become disorientated and had then “fallen some distance”.
“The young guy who took the initial fall had stumbled - on that kind of steep ground once a fall starts it’s very difficult to control it,” he told the BBC.
“The second guy had taken a tumble when he went down to see if his friend was OK.
“He was suffering from pain in his hip area and leg area and we were concerned that there may have been additional internal injuries along with that.”
Mr Watson said the part of the mountain where the men, believed to be in their 20s, fell was a “fairly steep, rocky area”, which is popular with rock-climbers.
“Unfortunately they found themselves on difficult ground and they really weren’t up for that kind of terrain. There’s also an element of bad luck.”
The first casualty was treated for multiple injuries and prepared for evacuation and due the to the severity of injuries, a Coastguard helicopter from Holyhead was requested and took him to hospital.
The second casualty was prepared for a stretcher evacuation by ambulance but his condition deteriorated and another helicopter evacuation was requested, this time a Coastguard helicopter from Dublin.
A total of 18 members of the MMRT ended their mission at 10.30pm.