He was a familiar face in the neighbourhood around Toa Payoh Lorong 4 and 5, usually sitting at a coffee shop on his own. Occasionally, the man in his 60s would greet other residents, said one shopkeeper.
But this year, his demeanour changed and he started behaving aggressively towards other people.
Residents and workers in the area spoke about him in hushed tones to The New Paper yesterday, describing him as a neighbourhood menace who would hurl vulgarities at strangers.
On Tuesday afternoon, the man's aggression turned violent when he allegedly attacked another man in his 60s at a food centre at Toa Payoh Lorong 4 with a pair of scissors, seemingly for no reason.
One witness, drinks stall owner Madam Liu, 62, told TNP in Mandarin: "The victim was just sitting there minding his own business when he was suddenly stabbed by this man.
"He's known around here. People tell me he's crazy."
Another witness, known only as Madam Hong, told Chinese daily Lianhe Wanbao that the victim remained calm and did not seek help.
Bystanders helped him only after they noticed that he was bleeding.
His assailant walked away, leaving behind a pair of shades and a spilt cup of coffee where he had sat, Madam Hong said.
Mr Joe Kwan, 57, a regular at the coffee shops in the area, said: "He was gone by the time the police arrived. There was blood on the victim's face and all over the floor. His shirt was soaked in blood."
The assailant returned to the scene after changing from his green T-shirt to a black polo shirt and pretended to be a bystander, said Mr Kwan.
Recalled the technician: "Three aunties standing nearby started shouting, 'He's the one, he's the one!' They turned to me and told me to catch him. So I did."
He restrained the man by holding on to his shirt until police officers, who had gone elsewhere to investigate, returned to the scene 15 minutes later.
"He kept wanting to leave but didn't really struggle. I said to him, 'If you want to be here, don't disturb the peace. Wait for the police.'"
A police spokesman said they received a call at about 2pm and arrested a suspect for voluntarily causing grievous hurt. Investigations are ongoing.
A Singapore Civil Defence Force spokesman said the victim was treated for minor injuries but refused to be taken to hospital.
Around two hours later, he called for an ambulance from his home after complaining of discomfort. He was taken to Tan Tock Seng Hospital, the spokesman said.