1900 A.D. Amur River, Manchu Empire
During the height of the Boxer Rebellion, Qing forces, Chinese militias, and Manchus strived to drive Westerners and Japanese out of the Qing Empire as a protest to imperialism and Christianity. In Manchuria, Manchu Bannerman—supported by Han Chinese Honghuzi guerillas and anti-foreigner militias—fought against Imperial Russian troops who had launched a full-scale invasion using more than 200,000 troops. Qing and Russian forces especially fought on the Amur River and while the Qing showed mercy to most Russian civilians they encountered, the Russians massacred and looted entire villages and even killed all of the Chinese living in the Russian trading city of Blagoveshchensk (this greatly angered the Honghuzi guerillas and led to them supporting Japan during the Russo-Japanese War). The most notorious incident was the annihilation of the "64 Villages East of the River"—a group of villages inhabited by Manchus and Chinese that was completely massacred by Russian troops when the inhabitants were either killed or driven in the Zeya (in Manchu: Jingkiri) River. Although this remained a contested issue in Sino-Russian relations for a long time, it was eventually resolved in the 1991 Sino-Soviet Border Agreement. However, there is a secret report that was handed to the Chinese dignitaries by the Soviets that was eventually leaked by Chinese hackers (the government claims it's a hoax). The report reads:
In 1900, Russian Imperial troops were ordered to massacre Manchu and Chinese inhabitants due to the possibility of them being a fifth column. However, when troops were sent to massacre inhabitants living in a group of 64 villages, our soldiers reported something peculiar. It seems that the villages were in utter chaos due to some sort of infection and that there were reports of cannibals running amok. Most disturbing is that these cannibals actually seemed to be regular Manchus and Chinese and they seemed to be feasting on their brethren. The soldiers massacred every villager cannibal or not—they could easily tell the cannibals apart due to their moaning. The cannibals seemed difficult to kill so the commander decided to drive all of the villagers into the river where they would surely freeze to death.
This raises the questions of where the "cannibals" (which were in all likelihood the living dead) went after being driven in the river and if they ever encountered other humans.