The father of a man from Plymouth who was part of a group mauled by a polar bear in the Arctic said what happened was "inconceivable".
Peter Reid said his son Mike, 29, shot the bear on the trip to Svalbard in which a 17-year-old boy died.
Mr Reid said doctors treating his son's head and neck injuries described them as not life-threatening but "serious".
Five people were mauled. Of those, Horatio Chapple, 17, from Wiltshire, was killed and the other four injured.
Scott Bennell Smith, 17, from south-east Cornwall, who goes to Devonport High School for Boys in Plymouth, was also one of the injured, the school confirmed.
The trip for 80 people was organised by the British Schools Exploring Society, a youth development charity based in London.
The attack on the campsite, near the Von Post glacier, about 25 miles (40km) from Longyearbyen, took place early on Friday.
Mr Reid, 65, said his son, who is also known as Spike, had volunteered for the expedition and had taken three weeks' holiday from his job at the Royal Geographical Society to take part.
He was one of the team leaders responsible for science experiments and had also been involved in training.
Mr Reid said: "It's what he loves to do.
"He was so excited to be going when we spoke to him four days ago.
"We were shaken by the news, but we have a son alive and under very good medical care in Norway.
"There's a family in Wiltshire who have lost their son. For us, their grief must be unimaginable."
Mr Reid said the incident had come as a complete shock.
He said: "In all honesty, we were more worried last year when he went to Afghanistan to climb.
"This was such a rare and unlikely event, it was inconceivable.
"If he is medi-vacced back to Britain, we're very keen that he comes to Derriford Hospital [in Plymouth]. We want him in our local excellent hospital if we can."
The 29-year-old was able to send an email to his family on Saturday, Mr Reid said.
Mr Reid said: "He told us the bear attacked the tent with three people in it, and he and another leader went to help and were viciously attacked by the bear.
"He managed to get away, ran to get a gun and shot the bear."
He added that his son wrote that he was "completely devastated" at Horatio Chapple's death.
Scott Bennell Smith has been described by his head teacher Kieran Earley as an "intelligent, bright, courageous young man".
Mr Earley added: "His family are relieved he got away with the injuries that he has. It was a huge shock for them.
"We're shocked too, as the school has a strong community. But he's coming back to Plymouth and we hope he'll make a good recovery."
Polar bears are one of the largest land carnivores, reaching up to 8ft (2.5m) and weighing 800kg (125 stone).
Earlier this year, the governor's office warned people about potential bear attacks after several were spotted near Longyearbyen.