A minor dispute over a game of Chinese chess led to the death of an elderly player in Kwai Chung yesterday, the city's second murder in a week.
Police arrested a 69-year-old neighbour in connection with the latest killing.
Meanwhile, officers are still looking for the boyfriend of a nightclub hostess, Wang Rong, 30, whose body was found in a suitcase floating in Victoria Harbour last week.
Chan Kuen-ching, 68, was playing chess with his neighbour in a park outside Block Five at Kwai Shing West Estate, Kwai Chung, when the confrontation happened at 1.20pm on Tuesday.
'A trivial matter allegedly led the suspect to punch the victim in the chest several times,' a police investigator said.
Chan, who had a history of heart problems, fell to the floor and passed out.
A witness called police and the alleged attacker fled before officers arrived.
Chan was taken to Princess Margaret Hospital, where he died early yesterday. Police have classified the case as murder and a postmortem examination is planned to determine the exact cause of death.
A retired government driver, Chan is survived by his wife, four daughters and one son.
The alleged attacker was arrested at his home in Block Five at 4am yesterday. He was being detained at Kwai Chung police station for questioning last night and no charge had been laid.
The suspect and victim lived in the same building and occasionally played chess together, police said. Last Wednesday, the body of Wang Rong, also known as Coco, was found in a suitcase floating in Victoria Harbour. It appeared she had been dead for four to seven days.
She was last heard from on March 25, when she claimed in a phone call that her boyfriend was attacking her.
Closed-circuit video in the Jordan apartment building where they lived showed a man, believed to be her boyfriend, leaving with a suitcase at 2am on March 26.
Police are looking for the boyfriend, nicknamed Monkey. He has fled Hong Kong and police will seek help from other law enforcement agencies to track him down.
Two murders were reported in the city in January.
The number of homicides that were recorded in Hong Kong last year, compared with 35 in 2010 and 47 in 2009