Chongqing police are questioning the girlfriend of serial killer Zhou Kehua as they investigate the possibility of other crimes and try to recover stolen money.
Zhang Guiying is 20 years old and rents a room in Chongqing, the Hong Kong-based Wen Wei Po newspaper reported yesterday.
A China Central Television report said Zhou would contact her before and after each robbery.
Zhou killed 10 people in the past eight years in three provinces, police said.
A previous death toll of nine was updated yesterday after it was confirmed Zhou was the killer of a sentry outside a barracks in Chongqing in 2009.
Police are also trying to ascertain the whereabouts of the rifle he stole that day.
"He would tell his girlfriend his thoughts on the robberies and the details of the crimes," the newspaper reported.
Minutes before Zhou opened fire on police in the alley where he was to die, he was seen talking on the phone.
Police monitoring the call said Zhou was telling his girlfriend about "a big one again" after he had shot dead a woman and wounded two other people outside a bank last Friday and made off with 70,000 yuan (US$11,000).
After a resident told police that Zhou had been seen in a shopping mall in Chongqing, police strengthened patrols in the city, which finally led to the encounter with the killer.
Instead of hiding in the dense mountain areas of Chongqing, Zhou strolled along busy downtown streets and even went to see a movie, according to media reports.
Police said Zhou had stolen more than 550,000 yuan during his deadly robbery spree.
The money was spent "mainly on his family," according to media reports.
Zhou's mother lives alone. Her husband died last year.