He callously beat the teenager to a pulp.
Even when his victim fell unconscious, Jeron Liew Wei Jie, 19, continued to hit him.
Five days later, the young man he assaulted died from his injuries.
Yesterday, Liew admitted to one count of voluntarily causing grievous hurt to Mr Kelvin Gan Teck Xiang.
The prosecution described the attack as one of the worst assault cases ever.
According to court papers, Liew was at a club in Selegie Road at about 2am on May 24 last year.
He ran into Mr Gan, 18, a Malaysian, and his friends. Liew chatted with the group but felt that during the conversation, Mr Gan was boasting that he was from a gang.
Liew challenged Mr Gan to a fight but he refused and stepped away to make a phone call.
Suspecting that Mr Gan was making a phone call for "backup", Liew grabbed his collar and led him into an alley.
He punched Mr Gan's face and Mr Gan fell unconscious.
Despite that, Liew yanked him up by his collar and challenged him to hit him. He then slapped Mr Gan in the face twice.
But he got angry when Mr Gan did not wake up so he threw the man to the ground, causing him to hit his head on a kerb.
Liew also kicked Mr Gan's head before he was pulled away by his friend.
He and his friend then went for supper.
Meanwhile, Mr Gan's friends carried him into a taxi and took him to a hotel.
They thought he was merely asleep but later realised something was wrong, so they called for an ambulance.
Mr Gan was rushed to the Singapore General Hospital at about 9am. He was found to have head injuries, a skull fracture and a blood clot in his brain. He also slipped into a coma.
Despite surgery and medical therapy, his condition did not improve, prompting his family to withdraw care.
Mr Gan died at 5.30pm on May 29.
His ITE College West schoolmate told Chinese newspaper Shin Min Daily News that she and Mr Gan were out with a group of about 10 friends that night. However, she said the group has not spoken much to each other since their friend's wake.
In court yesterday, Liew also admitted to hurting and robbing a foreign worker on Jan 16, 2015, with two friends.
At about 12.30am, Liew - along with Louis Chin and Liao Bang Xiong, both 19 - ambushed lorry driver Balasubramanian Sureshkumar, 29, an Indian national, at a pathway near the Upper Jurong Road canal.
They covered his mouth, punched his head and stomach, pushed him to the ground and held onto his arms and legs.
Chin and Liao then grabbed Mr Balasubramanian's two mobile phones, a Samsung and a Nokia worth a total of $370, and fled.
Liao later threw the Nokia phone away, sold the Samsung phone for $150 and spilt the money with his two friends.
Chin and Liao have been sentenced to reformative training, the court heard.
A month after the robbery, Liew was arrested for consuming Ice.
He told the authorities he had been consuming Ice since late 2013, when he was about 17.
Yesterday, Liew pleaded guilty to one count of drug consumption.
Four other charges - two counts each of possessing cigarettes when he was under 18 and possessing knives without lawful authority - were taken into consideration for sentencing.
Liew's mother told Shin Min Daily News after yesterday's hearing that her son had been listless.
She added that the last time she and his family visited Liew, who is in remand without bail, he had told them not to worry and that he would take care of himself.
DPP: Attack 'alarming in its savagery'
This was one of the worst cases of voluntarily causing grievous hurt, said Deputy Public Prosecutor Sarah Shi in her submissions yesterday.
DPP Shi said Jeron Liew Wei Jie's use of violence on Mr Kelvin Gan Teck Xiang was "unprovoked, gratuitous and alarming in its savagery".
When Mr Gan refused to fight, Liew launched a vicious one-way attack - with three sets of blows dealt after Mr Gan became unconscious.
She added that Mr Gan did not retaliate at any point.
"The most striking aggravating factor in this case is that the accused had caused (Mr Gan's) death, the most serious consequence that could result," she said.
DPP Shi also pointed out that this was not Liew's first brush with the law - he was sent to a juvenile home for property offences in 2011, jailed three weeks for voluntarily causing hurt in 2013 and jailed a week for affray in 2014.
DPP Shi called for Liew to be jailed nine years with 24 strokes of the cane for all his offences.
Defence counsel Kalidass Murugaiyan said in mitigation that this was not among the worst cases.
He pointed out that Liew had not assaulted Mr Gan with a weapon or while in a group.
Mr Kalidass said Liew had lost control that night and his bad blood with Mr Gan stemmed from his friend's dispute with the victim.
He called for Liew to be sentenced to reformative training or five to six years' jail.
District Judge Lim Keng Yeow said he was not persuaded that reformative training was appropriate for Liew's crimes.
The judge adjourned the case to April 29 for sentencing.
This article was first published on April 19, 2016.
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