After nearly a year of delay, a lengthy coroner’s inquest is to begin Monday into one of Hong Kong’s most mysterious crimes – the apparent ambush by one Hong Kong police officer of two of his colleagues.

Just after 1 am on March 17, 2006, an off-duty Hong Kong Police constable named Tsui Po-ko killed one of his colleagues and wounded another with a rusty revolver in a Tsim Sha Tsui underground walkway. He fired three bullets, one of which struck Constable Sin Ka-keung in the face. Sin survived but other two hit Constable Tsang Kwok-hang in his left leg and face, killing him. But before he died Tsang apparently returned five shots of his own killing Tsui.

At least, that’s the story the Hong Kong Police told at the time. But long after the shootings there are still no clear answers as to what transpired that night.

While the Hong Kong Police have one of the better reputations among law enforcement agencies in Asia, a troubling series of recent incidents – the March ambush being the best known – have raised questions of possible corruption and feuding in the ranks. Three officers died last year in shootings involving other officers. A fourth committed suicide while facing allegations of bribery.

The inquest, scheduled to last 37 days, may finally shed some light on at least one of the incidents but it is curiously late and some have called for an independent investigation, especially given Hong Kong’s highly publicized and vigorous past approach to police corruption.

Mass protests erupted in 1973 when a police superintendent under investigation for amassing millions of Hong Kong dollars in cash used his police pass to get on an airplane and leave town. That incident finally uncovered a web of corruption in the police force of the time. The British colonial government enacted strong anti-bribery laws and created an independent watchdog commission called the Independent Commission Against Corruption, which has unprecedented powers to arrest suspects and seize assets, and which has been credited with cleaning up the police force. However, critics say the ICAC, as it is universally known, has concentrated on low-ranking bureaucrats and police officers and has not gone after more powerful figures.

But in this case there has been no independent inquiry and though the inquest may be revealing, its scope may be too narrow for the whole story to emerge. The inquest will also examine the events of two other killings that police say are connected with the Tsim Sha Tsui incident.

The common link, police say, is that rusty revolver. It was stolen along with twelve bullets from Constable Leung Shing-yan after it was used to kill him when he responded to a phony noise complaint in a housing estate in March 2001. The same gun was apparently used six months later in the murder of security guard when a masked man robbed a Hang Seng bank branch of about HK$500,000.

After finding the missing gun by Tsui’s side, police all but decided they had solved the three cases in one swoop. “There should be sufficient evidence to charge the suspect on all three [killings] had he been alive,” the Hong Kong Police security bureau said in a presentation to the Legislative Council Panel on Security on April 7, 2006.

Certainly, Tsui ‑ labelled by some in the media as a “Devil Cop” ‑ appeared a likely suspect. Police said he had repeatedly been passed over for promotion, reportedly because of personality defects, even though he had performed well in qualification exams ‑ in 2000, he earned plaudits for placing second ahead of 2,105 of his colleagues. His alleged crimes were likely driven by “aggregated frustration,” Dennis Wong, a criminologist at the City University of Hong Kong, told the Associated Press. “Some people turn to crime to achieve social goals — such as status and power — when they can’t achieve them by legitimate means,” Wong explained to the news agency. “This happened in Tsui’s case. It’s very clear.”

Still, no matter how clear the case was, there was no hurry to open it up to an independent inquiry. That would have to wait, Deputy Secretary for Security Cheung Siu-hing said, until after the inquest, which would only take place after police had finished a “fair and impartial” criminal investigation.

“The police fully understand the public’s concern relating to the incident,” a police spokesman told the Legco security panel last April, “and have accorded the highest priority to its investigation.” In December, they finally completed that investigation. By the time the inquest is over, more than a year will have passed since the case of the rusty revolver.

In the meantime, constables Tsang, posthumously, and Sin were both awarded the Medal for Bravery, for “exceptional courage and gallantry of the highest order during a life-threatening situation”.

Others had different versions of the events surrounding the Tsim Sha Tsui gunfight. Various rumours and theories — many of them outlandish — circulated at the time; among the most credible was a scenario put forward by Niall Fraser in the Sunday Morning Post. Fraser linked the killings to illegal soccer gambling within the police force — the subject of a too-hot-to-handle investigation reaching as far back as 2000. (Triads are known to operate such gambling rings. One source, who had previously placed soccer bets with triads “two or three times”, told Asia Sentinel that police are among the main customers for triad-organised soccer gambling.)

Sources told the Post that the real reason Tsui was in the subway that night was to meet other police officers, probably to discuss gambling debts. They also suggested the soccer-betting link went as far back as the 2001 murder of Leung. The police have said there is no evidence of such a link.

Other reports attested to Tsui’s character. Though he had been passed over for promotion, he felt no bitterness because of it and was not suffering from work stress, one of his colleagues told reporters. The internal police magazine, Offbeat, had previously described him as dedicated and diligent. The 35-year-old, who had been a police officer for 13 years and had a wife and six-year-old daughter, had also been described as a fan of martial arts novels and a good marksman.

But the March killings are not the only mysteries dogging the Hong Kong police.

Just six months after the Tsim Sha Tsui shooting, Sergeant Wong Siu-pang was shot in the thigh by a fellow officer during a scuffle in Aberdeen. Wong and his patrol partner had confronted the constable, said by police to be suffering mental problems, after he fled a taxi while being accompanied home from hospital by family members. Wong survived but less than a month later, while jogging with friends at a sports ground, he dropped dead. His death remains unexplained, but a police spokesperson said the gunshot injury might have been a contributing factor. Police have not linked the Aberdeen shooting to the Tsim Sha Tsui shootings.

In September, Stephen Fung Kin-man, the former head of police anti-triad operations, jumped to his death from a housing estate apartment tower. At the time Fung, a 32-year veteran of the force, was on sick leave after attempting suicide in March. It is not clear from news reports when in March he made his first attempt, but Fung, then 49, reportedly had been questioned by the ICAC about his involvement in the case of Chan Tat-chee, the former chairman of China Sciences Conservational Power Ltd., who admitted in court last year to defrauding his firm of HK$63 million. A coroner later ruled no inquest was necessary in Fung’s case.