After 26 days delving into the circumstances surrounding the deaths of three police officers and a bank security guard, the Coroner's Court has been given a vivid image of a constable psychologically troubled by career setbacks which forced him to walk down a path of no return.
The inquest, which has so far heard evidence from more 100 witnesses, began with testimony on the brutal ambush of constable Leung Shing-yan as he was investigating a bogus noise complaint at Shek To House, Shek Wai Kok Estate, Tsuen Wan, on March 14, 2001.
He was shot five times at close range - three times in the head - and his revolver and speed loader with six bullets were stolen.
Along with bloodstain pattern expert Cheung Kam-yin's meticulous analysis of the crime scene, as well as pathological details of the autopsy on Leung, the court heard grim details of how the officer unknowingly walked into a death trap.
According to pathologist Nam Wai- man, Leung had put up a struggle before he was shot in the head and slumped to the ground.
He was then shot twice more in the head and twice in the back.
The second killing occurred on December 5, 2001 at Belvedere Garden, Tsuen Wan when a masked robber burst into a Hang Seng Bank branch and shot security guard Zafar Iqbal Khan who tried to stop him.
Khan was shot three times - with one fatal shot to his head, execution style. The robber fled with almost HK$500,000.
After comparing the bullet fragments found at the crime scene with the police "outstanding crime index," it was confirmed the same revolver had been used to kill Leung and Khan.
A shred of evidence obtained from constable Tsui Po-ko's home drew much attention. A note by his bed carried such phrases as "Peace and quiet only make things stop. Only conflicts, war and confrontation can make new life."
Coroner's officer Arthur Luk Yee- shun did not explain these phrases and focused instead on the 27 home videos found in Tsui's flat, comparing them with images recorded by the security video installed at Belvedere Garden during the bank heist.
The spotlight immediately fell on the red long-sleeved sweater and Mizuno sneakers worn by Tsui in the home video - attire similar to that of the bank robber.
Chen Feng told the inquest he met Tsui after a motorcycle festival and had given him the sweater as a souvenir.
Then came the testimony of constable Sin Ka-keung, the sole survivor of the Tsim Sha Tsui underpass gunbattle on March 17 last year.
Sin and constable Tsang Kwok- hang were ambushed in the underpass at the junction of Austin and Canton roads. Tsang suffered one gunshot wound to the head and died, while Sin sustained gunshot wounds in the face and leg.
Sin had testified he saw a man lurking on the northern stairs of the subway before he was shot in the face.
Sin said the attacker then tried to snatch his revolver. He grappled with the man and fired two shots before both of them slumped to the floor.
The wallet found on the man revealed he was off-duty constable Tsui Po-ko, who was also killed.
Under Tsui's body, investigators found a gun that was later identified as the one stolen from Leung. However, while evidence linked the gun to the three incidents, a forensic expert said he could not say with certainty the gun found under Tsui had fired the shots that killed Leung and Khan since it was rusty.
As family members and colleagues of the dead policemen came forward to testify, more personal side of Tsui emerged.
Tsui's father and a younger brother defended him vigorously, claiming they had never seen him using his left hand - a reference to the Tsuen Wan bank robber who fired the gun with his left hand.
Tsui Po-wan, Tsui's younger brother, told the court they grew up caring for each other after the family moved to Hong Kong.
He described his brother as a friendly, thrifty person who was determined to succeed.
He said Tsui had complained about police work, saying it was repetitive and boring.
The inquest also heard Tsui was using his friend's flat in Yau Ma Tei as his correspondence address in dealings with banks and investment contacts, had lost HK$370,000 in those investments and had tried to hide this from his wife.
Tsui's colleague Lee Ngai revealed he and Tsui had patronized massage parlors and karaoke bars and had sought sexual services.
Lee also disclosed Tsui had, on one occasion, placed a HK$75,000 bet on a football match and won HK$210,000.
According to his superiors, Tsui had passed the sergeant promotion examination in 1998 but was rejected for an interview.
He went on to take the same exam three more times, scoring high marks.
The court further heard Tsui made a scene at a bridal shop after his 1997 wedding when the shop withheld his deposit. He was arrested but later released due to lack of evidence.
Part of the hearing focused on Tsui's behavior and personality.
He won the "silver whistle" for being an outstanding student at the police training school and was a superb marksman. But his stubbornness and difficulty in communication led to poor relationships with his colleagues and superiors.
Witnesses described his behavior as odd, excessively handing out parking tickets and shouting anti-communist slogans while crossing the border to visit the mainland.
Representing Tsui's mother, barrister Arthur Yip Chi-ho made numerous objections when the Coroner's officer tried to look into Tsui's personal life, saying this amounted to an intrusion of his privacy and had no bearing on the case.
His objections were all struck down.
Two overseas criminologists went further, one saying his behavior fitted into the mould of a "serial killer" and that he later suffered from god-like delusions.
US Federal Bureau of Investigation criminal profiler James McNamara told the court Tsui's behavior fit into most of the definitions for people suffering from schizotypical personal disorder.
Roderic Girth Broadhurst from Queensland University of Technology said Tsui's personality profile matched that of a serial killer.
Referring to the poem found in Tsui's home, Broadhurst said it showed Tsui believed he was destined to change the world, probably tried to rise above his self-perceived unremarkable life by playing G`od - in the form of taking lives.
"He needed to transcend from the ordinary to behave more like a god. It means by taking another's life, the offender adopts a god status. Only God takes life; he put himself on the same plain as that of a god."
Police clinical psychologist Ephraem Tsui Pui-wang said Tsui may not have intended to kill Leung in 2001 and may have merely wanted to embarrass the police force by snatching a revolver from a fellow policeman.
But as guilt was building up, he began to rationalize his murderous action.
The inquest will continue Tuesday with a police superintendent of the Criminal Intelligence Bureau testifying on the financial status of the key figures involved in the three incidents.