Police in China's Hebei province have arrested a man suspected of murdering at least 65 people, local media say.
The man, identified as Yang Zhiya, was apprehended as police inspected an entertainment venue in the northern city of Cangzhou on 3 November.
They later discovered that he was wanted for murder in three other provinces.
Correspondents say this could be the deadliest case of individual mass murder in China's recent history.
Such cases are not widely reported in China as the country sees itself as being mostly free of the types of violent crimes often reported in the West.
The media said that Yang wanted to take revenge on society after being dumped by his girlfriend.
She had left him because of previous sentences he served in prison and reform camp for robbery and rape.
Yang was arrested in a routine operation because he appeared suspicious.
But police found that he was wanted in the provinces of Anhui, Shandong and Henan, as well as in Hebei itself.
Yang's alleged victims were said to be mainly farmers.
"His methods were extremely cruel," Guangzhou Daily newspaper said in an article on Saturday.
"He didn't leave survivors, and more than a few families were exterminated by his hand."
Beijing's Ministry of Public Security, which has some jurisdiction over cases involving several provinces, congratulated Cangzhou police on their success.
But the ministry made no further comment on the arrest.