A Canadian man has been killed during a rescue operation after he cut an endangered whale free from tangled fishing lines.
Joe Howlett succeeded in rescuing the whale, only to be struck by it moments later as it flipped into the water.
He was a lobster fisherman by trade and a founder of the whale rescue group on Campobello Island, New Brunswick.
Friends told the Canadian Press he had saved some two dozen whales over 15 years.
Mackie Green, a friend of Mr Howlett who had founded the rescue team with him, said: "They got the whale totally disentangled and then some kind of freak thing happened and the whale made a big flip."
"Joe definitely would not want us to stop because of this," he added. "This is something he loved and there's no better feeling than getting a whale untangled, and I know how good he was feeling after cutting that whale clear."
The animal was a North Atlantic right whale - an endangered species that may grow to about 15m (50 feet) in length and weigh up to 70 tonnes.
The species is "critically endangered", with about 500 left alive, according to the US National Oceanic and Atmospheric Administration.
Seven were found dead in Canada's Gulf of St Laurence in the last month - a significant blow to the global population.
Mr Howlett was on board a government response vessel at the time of his death.
The Department of Fisheries and Oceans said he had rescued another whale days before, on 5 July. Rescuers like Mr Howlett had "immense bravery and a passion for the welfare of marine mammals", it said.
"There are serious risks involved with any disentanglement attempt. Each situation is unique, and entangled whales can be unpredictable."
Mr Howlett lived on Campobello Island, a small community on the border withy the US, where locals have been paying tribute to the well-known rescue worker.
"There's only 850 people here on Campobello Island now and Joe was a very lively character, he had a great sense of humour," mayor Stephen Smart told the Canadian Broadcasting Corporation.
"Everybody knew Joe Howlett and everybody respected Joe Howlett... it's a big blow."