The 23-year-old, named locally as Vadim Klabukov, had taken tourists to a stream filled with red salmon.
On his return he realised he had left his bag and decided to make his way back to the area alone.
The ranger, who had only started working at South Kamchatka nature reserve in far east Russia this summer, unsuspectingly went close to the animals’ food stash.
Two large bears attacked him leaving him with no time to use the gun or knife he had with him, reports The Siberian Times.
His gnawed bones were reportedly found at the site.
It is understood the carcass of another bear was also found – believed to have been killed by the same pair of beasts.
Local wildlife chief Vladimir Gordienko said: “The situation was aggravated by the fact that the animals were near their prey – another dead bear, and, apparently, protected their food.
“This is a rare case when, with an abundance of feed, in this case fish and bear carcass, bears treat people as prey.”
The nature reserve previously withheld details that he had been killed and eaten by two bears.
Though they have now offered Klabukov’s family their condolences.
However, they insist he had died as a result of not following safety regulations.
A spokesperson for the reserve said: “Vadim got a job in the nature reserve this summer, as soon as he graduated from Irkutsk Agrarian University.”
On Saturday, it is understood he left the Ozerny area without saying a word to his colleagues and bosses.
The Investigative Committee has launched a preliminary check into his death.
Kamchatka brown bears can grow up to three metres tall and weigh up to 650kg.
The area in Russia is dangerous because the bears feed and attack if they think their prey is at risk.
Attacks on humans are usually very rare.
The Kamchatka breed of bear is often renowned as among the most prized trophies for the Russian hunting industry.
Hunters have often paid more than £9,000 to kill them.
(Additional reporting by Will Stewart)