On 2 September 2007, 20-year-old Corporal Dave Teo Ming (张铭 Zhāng Míng), a full-time National Serviceman from the Singapore Armed Forces (SAF), went absent without official leave (AWOL) from Mandai Hill Camp and deserted his unit with a SAR-21 assault rifle and eight live 5.56mm rounds. Teo was arrested at a shopping mall in Orchard Road after a 20-hour manhunt and he was charged with possessing a rifle and live rounds of ammunition under the Arms Offences Act. It was alleged that Teo escaped camp and intended to use the rifle to murder his ex-girlfriend and several other people he hated in his life. In July 2008, Teo was put on trial, convicted and sentenced to nine years and two months' jail and 18 strokes of the cane. During February of that same year, Teo's accomplice Ong Boon Jun (王文俊 Wáng Wénjùn) was also given a sentence of 78 months' jail with six strokes of the cane for consorting with Teo who illegally possessed a firearm.

AWOL incident and manhunt On 2 September 2007, 20-year-old Corporal Dave Teo Ming of the 1st Singapore Infantry Regiment of the Singapore Armed Forces went missing from Mandai Hill Camp. His disappearance was only noticed at 11.59 pm, and it was also discovered by the army personnel that Teo's rifle and five bullets, which were issued to him for guard duty, were also missing. As a result, the military police were alerted to Teo's desertion and they conducted a search within the camp premises. After the search failed to locate Teo, the Singapore Police Force took over the case and thus initiated an island-wide manhunt, and over 200 police officers participated in the manhunt to capture Teo, although this operation was conducted in secrecy and away from the public eye.

About 20 hours later, at about 8pm on 3 September 2007, Teo was finally arrested at a shopping mall near Orchard Road; the police discovered him at a toilet in the mall's third floor, just when Teo managed to load the rifle. The police managed to recover the rifle and five bullets; they also recovered three more live rounds of ammunition which Teo stole from the camp back in August 2007 during a live-firing exercise. A 40-cm long knife was also recovered in Teo's possession. Based on first-hand investigations, the police managed to uncover that while on the run, Teo and a friend had stayed at a Geylang hotel and asked for a Thai prostitute. The same friend was also arrested on suspicion of having accompanied and abetted Teo during his desertion. The police announced to the public regarding the incident, and they admitted that this manhunt was not publicized out of consideration for the operation to be carried out safely and successfully, and for fear that it may only provoke the suspect into resorting to worse measures. The Ministry of Defence (MINDEF) also stated in a media statement that MINDEF and the Singapore Armed Forces (SAF) would cooperate with the police in investigating the case.

In response to the arrest of Dave Teo, his 70-year-old grandmother Tan Ah Hoon, who was his primary caregiver after his parents' divorce, was in a state of anguish over her grandson's actions, especially since she already lost one of her grandsons (Teo's younger brother) to a car accident in 2001. Tan died from liver cancer in late 2007 while Teo was still in remand awaiting trial for the AWOL incident he perpetuated. The public was also shocked at the desertion, and it was also speculated that Teo had gone AWOL due to a failed relationship, although a source revealed that Teo, who was originally supposed to end his National Service (NS) in October 2007, had performed well in his NS duties. Teo's army partner and superior also noted that Teo did not show any unusual behaviour during his time at the army camp, although the superior recalled that Teo was stressed about issues related to his ex-girlfriend.

The AWOL case of Dave Teo was the first time in 23 years where a National Serviceman had gone AWOL with a rifle and ammunition. The last such case happened on 6 August 1984, when 18-year-old Teo Yong Kuan, who came from the 30th Singapore Combat Engineering Battalion, was charged with stealing an AR-15 rifle and 30 bullets from Khatib Camp. Teo Yong Kuan, who admitted to all charges, was sentenced to five years' imprisonment and 12 strokes of the cane on 12 May 1986.

Criminal charges of Ong and Teo On 5 September 2007, 20-year-old Dave Teo Ming was officially charged in the Subordinate Courts with an unlawful possession of a firearm under the Arms Offences Act. His 21-year-old accomplice Ong Boon Jun was also charged in the same court, and he faced one count of consorting with Teo while being aware that Teo possessed a firearm. Teo, who did not wish to plead guilty, faced a sentence of between five and 14 years' jail with the mandatory minimum of six strokes of the cane for the charge he faced in court. A week later, Teo faced two additional charges on top of the firearms charge he first received back in September; mainly one count of possessing bullets illegally and one count of using a knife to threaten his ex-girlfriend in an unrelated case.

Ong originally was offered a S$50,000 bail, but due to his family's poor financial situation, they were unable to raise the amount on short notice and Ong thus voluntarily gave up bail, and thereafter remained in remand. On the other hand, Teo was not offered bail as he still posed a great risk to public safety should he ever be freed, and the possibility of him contacting other witnesses was also among the factors considered in refusing Teo's request for bail.

In October 2007, Teo's case was transferred to the High Court for trial hearing on a later date. During a preliminary hearing on 27 November 2007, Teo's counsel sought a reduction of his charges, likely on the grounds of diminished responsibility, and the counsel was earlier given time until 21 December to submit psychiatric evidence to the court. Ong's counsel similarly asked the court to reduce their client's charges.

In January 2008, Ong's case was scheduled to be heard separately in the Subordinate Courts, while Teo's case would move forward for hearing in the High Court as approved in March 2008. On 14 February 2008, it was reported that Ong would plead guilty to the charges against him, and his defence lawyer Amolat Singh planned to argue for the minimum penalty of five years' jail in mitigation during the upcoming trial.

In April 2008, Teo was scheduled to stand trial on 7 July 2008 for the charges preferred against him in the AWOL incident, after the Subordinate Courts ruled in the preliminary hearing that a prima facie case had been established against Teo.

Conviction and appeal of Ong Boon Jun On 26 February 2008, Ong Boon Jun, then 22 years old, pleaded guilty at a district court to one count of consorting with Teo while having the knowledge that he possessed a firearm. Ong was sentenced to years' imprisonment (or 78 months' imprisonment) and six strokes of the cane by District Judge Liew Thiam Leng, who stated that no compromise should be made to the safety of the public and the security of the nation, and as a former National Serviceman who knew well the need for safeguarding public safety, Ong had plenty of opportunities to report Teo to the police, especially with the knowledge that Teo wanted to commit firearm robbery. Ong's adoptive mother and father were allowed to speak to Ong after his sentencing, and Ong "inconsolably wept" as he apologized to his adoptive parents, and his adoptive mother consoled him, advising him to learn his lesson. On 1 March 2008, it was confirmed that Ong would appeal against his sentence.

During Ong's appeal hearing at the High Court, Amolat Singh argued on behalf of Ong that he was merely a reluctant accomplice who had been "shell-shocked" by the sight of Teo's rifle and he was afraid of his safety and did not want to unnecessarily excite Teo into doing something rash with the weapons. He also asked the jail term of Ong should be reduced on the grounds that it was manifestly excessive. In rebuttal, the prosecution argued that Ong had ample opportunity to dissociate himself from Teo but he did not, and there was nothing to support Ong's claims of fear as he chose to stay in the same hotel as Teo for four hours with the rifle being close to him prior to Teo's arrest.

In the end, Ong's appeal was dismissed by Justice V. K. Rajah on 20 May 2008. Justice Rajah stated that while it was understandable for Ong to not report to the police but he did wrong all the same and the law should be equal to anyone, including Ong. Justice Rajah stated that by having the knowledge that Teo planned to use the rifle for a crime and yet not taking steps to alert the authorities, Ong's culpability in this case was heightened and he should be punished, in order to send a signal that anyone who chose to do nothing would face the full force of the law.

Background of Dave Teo Ming

Born in August 1987, Dave Teo Ming was likely the second of four children in his family, and he had one younger brother, one older brother and one younger sister. According to news sources and court documents, Teo had an unhappy childhood and he came from a dysfunctional family background. Teo's father often went to prison for various offences, and as of the time when Teo was arrested for desertion, Teo's father was incarcerated for drug trafficking. Teo's mother heavily gambled and neglected her two sons, relentlessly and cruelly abusing Teo and his younger brother, often beating them up whenever she lost money, and she even did so for no reason on numerous occasions. Teo's mother would also throw chairs at him constantly. According to Teo, he told his psychiatrist that his mother would repeatedly cane him until the cane broke and serious bruises were left on his back. Teo's grandparents and aunt stated that the trauma of abuse had affected him gravely.

Eventually, Teo's parents divorced when he was merely seven, and his mother abandoned the Teo brothers and took Teo's younger sister, Teo Ping, away. Therefore, Teo and his brother lived with their paternal grandparents, but he was abused by his uncle. When Teo was 14, his younger brother Teo Zhong Yi, died in a car accident 2 days before his twelfth birthday in 2001, and Teo was extremely devastated over his brother's death, as he and his brother shared a close relationship. The death of his brother was a great blow to Teo, causing a downward spiral in his life and disciplinary problems. He also began to isolate himself from his family, felt depressed, and was often filled with anger and hate towards people around him. Teo often played truant, and he eventually dropped out during his third year of secondary school.