One of the seven people killed in the mass murders at an apartment in Panyu, Guangdong, is believed to have been a Hong Kong member of the 14K triad society.
Sources also say that Ng Chun-fai was probably killed as part of a dispute over arms trafficking from the mainland.
The final destination of the weapons is not clear but Ng is said to have had links with Macau casinos. His official occupation has been given as a car dealer.
The victims' identities were revealed in mainland newspapers yesterday after coroners examined their bullet-riddled bodies.
Ng, who owned the flat, his mother and sister, his girlfriend, surnamed Lee, Lee's mother, his driver's wife and a man surnamed Gong all died.
Ng and his sister were both Hong Kong residents, while his girlfriend and Gong were reported to be Australian and American citizens respectively.