Three people have reportedly been arrested over the shooting of a British helicopter pilot by elephant poachers in Tanzania.
The men were held by police in the East African country on Sunday over the murder of Roger Gower, the Agence France Presse (AFP) agency reported.
Mr Gower, 37, was helping authorities in Tanzania track the criminals when they fired on his aircraft on Friday, the Friedkin Conservation Fund (FCF) said.
He managed to bring the helicopter down in the Maswa Game Reserve, near Serengeti National Park in the country's north, but died from his wounds before he could be rescued.
Pictures posted online show the badly damaged remains of the helicopter, including a bloodied bullet hole in the pilot's seat of the aircraft, which lay on its side in the savannah grass.
In a message posted on its website, FCF founder Dan Friedkin said the organisation was "profoundly saddened by the loss of our dear friend".
He said: "Roger was killed while piloting a helicopter during a co-ordinated effort with the Tanzanian wildlife authorities to track down and arrest active elephant poachers. In the course of this action the poachers fired upon the helicopter and Roger was fatally wounded.
"We are committed to honouring Roger and his work. We are also committed to ensuring that those responsible for this attack are found and brought to justice. We believe that Roger can best be honoured by redoubling our commitment to protect elephants and our priceless wildlife heritage.
"This tragic event again highlights the appalling risk and cost of protecting Tanzania¹s wildlife."
Tanzania is fighting a bitter struggle to stop ivory poachers, a report last year saying 60% of its elephant population had been lost in the previous five years.
China is the world's largest market for illegal ivory, which has been thriving under the cover of legal ivory sales. Tanzania also last year charged a Chinese woman, Yang Feng Clan, 66, with smuggling 1.9 tons of ivory from the country between 2000 and 2014
Mr Gower was a former accountant who qualified as a pilot in 2004 and moved to Africa around two years later, according to a profile with his former employer Tropic Air Kenya. It also says he helped the British Army on exercises in the country.
In a Facebook post Tropic Air Kenya said it was "shocked and immensely sad" at the news that he had been killed "in the long and ongoing battle against elephant poaching".
It said: "Roger, only 37 years old, was a fantastic heli pilot in every way, and flew for Tropic Air for four years, leaving last August to pursue new flying ambitions ?#?Tanzania?. Bye Bye Rog .. you will be greatly missed. Our thoughts are with his family."