An endangered species himself, the 34-year-old Sumatran elephant patrolled the jungles of Bukit Barisan National Park on the island of Sumatra in western Indonesia on anti-poaching missions, and helped calm potentially dangerous wild elephants threatening to stampede.
But earlier this month, Yongki, who weighed 3.3 tons, was found dead, his 3-meter long tusks cut off. And the news has sparked outrage across the country and on social media.
On the morning of September 18, one of the elephant keepers in the park found Yongki's slumped carcass. There were no bullets in his body but his tusks appeared to have been cut off with a chainsaw, investigators say.
Initial test results indicate that Yongki was poisoned. No trace of the perpetrators has been found.
Photos of the elephant's body were posted online, and angry messages quickly appeared on Twitter using the hashtag #RIPYongki.
"Humans are (far more) savage than the wild itself, sometimes," posted one user named Santi Sundari.
The massive conversion of forest land for pulpwood and palm oil plantations, as well as the encroachment of people have threatened habitats for elephants and other wildlife in the region.
The World Wildlife Fund (WWF) estimates that there are between 2,400 and 2,800 elephants left in the wild in Sumatra.
But in some cases, angry local residents and farmers have killed wild elephants foraging for food on their plantations. And poachers, looking to cash in on the ivory, take advantage of these conflicts.
"They target both trained and wild elephants," said WWF Wildlife and Landscape Ecologist Sunarto, who uses one name, as is common in Indonesia.
"The peak of the killings was between 2012 to 2014. Yearly, about 15 elephants were killed."
For conservationists, Yongki's death again highlights the urgent need for action to protect this critically endangered species.
"Comprehensive investigation effort is required by the authorities to identify and seize the killer," said Anwar Purwoto, Director of Sumatra -- Borneo WWF Indonesia. "It's also important to take action to avoid another incident in the future."