However, the 27-year-old ex-convict Zainal Abidin Abdul Malik retrieved an axe from his black bag and used it to strike Boo on the head, which killed the 47-year-old policeman instantly.
Boo first joined the Singapore Police Force in 1973, and he gradually rose through the ranks, attaining the post of deputy OC of the Whitley NPP, a position he held from November 1989 until 1992, when he retired at age 45.
[4][5] On the early morning of 30 November 1994, both Boo and his partner, Corporal Muhaimin bin Mawasi, were at Newton Road carrying out their usual patrol duty when they noticed a man behaving suspiciously near Goldhill Plaza.
The officers approached the man (Zainal), who was carrying a black bag, and they inquired about his identity and asked for his ID card as part of the routine check which police should perform while on patrol.
Soon after the incident, a 24-year-old handphone exporter named Geoffrey Yeo Yap Hin (杨业兴 Yáng Yèxīng), who was driving to meet up with a friend for supper, spotted the suspect running from the crime scene and towards an open field around Khiang Guan Avenue.
Yeo, who was later commended by the police for his assistance in apprehending the killer, was shocked when he later realize the man was a murder suspect, but he nevertheless offered condolences to Boo's family.
"[12] Commissioner Tee also expressed that the police and prosecution would pursue a preliminary murder charge against the suspect, who had several previous convictions, for the killing of Boo.
The event was reportedly solemn and filled with heartbreak, especially when Boo's widow, who wept openly in public, had to be supported by her relatives throughout the ceremony.
Zainal Abidin committed another housebreaking offence in 1983, resulting in him being sentenced to three years of reformative training before he was released and given an additional one-year probation.
He stated that on that day itself, he wanted to go to a hotel (also his former workplace) at Newton Road to commit armed robbery, and therefore he packed up his black bag, which contained his axe, two knives, a hammer, torchlight, and a pair of gloves.
He presented that Zainal Abidin should not be held fully accountable for his actions as he had a delusional disorder that impaired his mental responsibility at the time of the crime, given that he had delusions of wanting to bomb several places in Singapore and assassinate both the Senior Minister and Prime Minister, and self-harm symptoms, as well as his own upbringing, his feelings of inferiority over his homosexuality and his hatred against the Chinese for being more successful than the minority races like Malays and Indians, which made him perceive that the police would often preferentially pick Malay people like him for routine spot checks instead of the Chinese or Indians.
DPP Tseng also argued that the prosecution's psychiatric evidence should be accepted as it showed that Zainal Abidin was not mentally abnormal at the time he committed the crime.
[37] In the judgement, JC Kan found that Zainal Abidin was not suffering from an abnormality of the mind when he killed Boo Tiang Huat, given that he did not have difficulty in planning how to commit robbery, was able to tell the difference between reality and imagination, and could think of how to escape.
[38] JC Kan also judged that should Zainal Abidin have had no intention to kill or seriously hurt the police officer and only meant to escape, he would have chosen to grab any non-threatening objects like his gloves or torchlight, or perhaps even show his fist to give the impression that he was taking something before fleeing.
On the same day, three other people - ex-prostitute Teo Kim Hong who killed her Malaysian friend Ching Bee Ing, Thai welder Thongbai Naklangdon who killed his compatriot and co-worker Suk Malasri, and Thai farmer Jeerasak Densakul who smuggled 2 kg of cannabis - were also executed at the same prison as Zainal Abidin.
[47][48][49][50] More than two decades later, on 3 August 2021, as a commemoration of the 200th anniversary of the Singapore Police Force, a medallion was issued to the families of policemen who died in the line of duty as a recognition of the fallen officers' contributions.