A long-standing battle between two factions of the notorious Wo Shing Wo triad society was behind a fatal chopping on Sunday, police say.
Four suspected triad members have been arrested in connection with the murder of a 30-year-old man, nicknamed Mouse Shing.
Mouse Shing was hacked to death by two masked men with an axe and a meat cleaver outside North District Hospital in Sheung Shui.
The four men, aged from 18 to 30, were picked up by police in Yuen Long and Sheung Shui.
Last night, they were being held for questioning and no one had been charged.
The suspects are alleged henchmen of the Wo Shing Wo faction leader nicknamed Yen Chai who, among others, is being hunted by anti-triad officers in connection with the brutal killing.
Police intelligence revealed that a Tsuen Wan-based faction headed by Yen Chai tried to extend its influence in Sheung Shui and the move led to confrontation with the Sheung Shui-based faction led by a man known as Hau Sai, according to a police officer.
"Their dispute has sparked a series of violent incidents and has lasted for a long time," he said.
Yen Chai and Hau Sai bear the rank of red-pole fighter - a senior triad member who acts as an enforcer.
"Yen Chai is a troublemaker. He likes to solve problems through violence," the officer said.
Mouse Shing, believed to be a henchman of Hau Sai, was ambushed by the two masked men about 1pm on Sunday as he left the hospital after treatment for a leg injury.
Walking with a cane, he was caught by the two attackers in Po Kin Road outside the hospital.
After hacking him to death, the pair fled in a white car before police arrived.
The victim suffered multiple chop and cut wounds to all four limbs and was taken to the hospital, where he was declared dead at 2.32pm.
A senior officer said police would step up surveillance of the two triad factions to prevent retaliatory attacks after the killing.
"Police will raid venues allegedly controlled by the two triad gangs, including illicit gambling dens and entertainment outlets, while searching for attackers in connection with the murder," he said.
The New Territories North regional crime unit is investigating the case.