SHENYANG, China/BEIJING (Yonhap) ― China said Monday it had lodged a protest with North Korea after a North Korean army deserter killed four Chinese citizens in an apparent robbery in the Chinese border city of Helong late last month.

The incident took place on Dec. 28 last year in the border town of Nanping in Helong, just north of the Tumen River overlooking North Korea’s North Hamkyong Province, a source with knowledge of the incident told Yonhap on condition of anonymity.

Asked about the incident, China’s foreign ministry spokeswoman Hua Chunying told reporters, “We have lodged a representation with the North Korean side and China’s public security authorities are dealing with the issue.” Hua declined to elaborate further.

The gun-wielding North Korean man killed the four Chinese citizens and injured another Chinese person at their homes during an apparent robbery, according to the source.

Chinese police and military authorities caught the suspect after a manhunt. The suspect has since been under investigation, according to the source.

Chinese authorities have not announced the incident and the country’s state-run media organizations also have remained silent.

“The Chinese authorities have ended a consultation with the North Korean side in dealing with the case and decided not to make the case public,” the source said.

It is not uncommon for North Korean soldiers or citizens to cross the border into Chinese towns and attempt robberies.

In December 2013, a North Korean defector in his 20s killed an elderly Chinese couple in the Chinese border city of Yanji and stole 20,000 yuan ($3,210). The North Korean defector was caught by Chinese authorities after fleeing to Beijing.