Bethan Davies and Robert Jesty were abducted on Friday in Virunga National Park, home to mountain gorillas.
"Ranger Baraka was critically injured whilst protecting two passengers and the driver of the vehicle they were travelling in, when it was attacked by armed assailants", a statement from Virunga National Park said.
Two Britons kidnapped in a national park in DR Congo have said they are "very grateful" after their release.
Earlier, tributes were paid to 25-year-old Ms Baraka, the eighth ranger to be be murdered at the park this year. She was one of the Park's 26 female rangers and was highly committed, showing true bravery in her work.
In peacetime, the Virunga National Park has barely fended off the local warlords and gangsters seeking to strip it off its valuable timber or the government officials and vested corporate interests seeking to exploit its oil.
"We wish to extend our sincerest condolences to her family, and our thoughts are with all those affected by this incident".
Soldiers at an Army base a few hundred yards from where the latest kidnapping took place were criticised for their slow response.
He said the park was protected by around 800 rangers but there were also estimated to be between 1,500 and 2,000 militia members in and around the park.
Virunga is home to about one-quarter of the world's remaining mountain gorillas, and the work of protecting them has proven unsafe.