The world's last male northern white rhino has died leaving only two females left to save the species from extinction.
The 45-year-old rhino named Sudan had been in poor health in recent days and was being treated for age-related issues and multiple infections.
A veterinary team made the decision to euthanize Sudan after his condition deteriorated significantly, the conservation group WildAid announced Tuesday.
Sudan lived in the Ol Pejeta Conservancy in Kenya, surrounded by armed guards in the days leading up to his death.
"He was a gentle giant, his personality was just amazing and given his size, a lot of people were afraid of him. But there was nothing mean about him," said Elodie Sampere, a representative for Ol Pejeta.
Researchers were able to save some of Sudan's genetic material in the hopes of successfully artificially inseminating one of the two females left, Sampere said.
"We can only hope that the world learns from the sad loss of Sudan and takes every measure to end all trade in rhino horn. While prices of rhino horn are falling in China and Vietnam, poaching for horn still threatens all rhino species," said WildAid CEO Peter Knights.
Correction: This story has been updated to clarify that Sudan was a northern white rhino.