A 39-year-old jobless man stabbed himself multiple times in the neck and chest before turning the knife on one of his tenants, a court heard.
Both the assailant, Lay Chee Leong, and his victim survived.
Lay, who suffers from substance use disorder with symptoms of psychosis and depression, then threatened to detonate a bomb in his flat.
He also said he would fill the unit with liquefied petroleum gas (LPG) before igniting the vapours so that everyone inside would die.
Yesterday, Lay was convicted on one charge of causing grievous hurt with a deadly weapon and one of criminal intimidation. He also admitted to one count each of criminal intimidation and attempted suicide. These will be taken into account when he is sentenced on Dec 15.
Lay, who has received at least 50 strokes of the cane for a string of previous crimes including robbery, lived with his parents in a flat in Yishun.
One room was rented out to three women from China, aged 20, 27 and 35, who worked together as electronic component assemblers.
At about 5.30am on March 23, Lay stabbed himself repeatedly in the chest and neck with a 22cm-long knife. He then called the police and said: "Commit suicide, OK never mind."
Lay then went to the tenants' room and kicked the locked door open. He then demanded the tenants' mobile phones as he did not want them to call the police.
Shortly after, he said: "Since I am already like this, it does not matter if I kill another one or two."
He also told the tenants not to open the door for the police or he would detonate a bomb inside the flat, said Assistant Public Prosecutor (APP) Lim Yu Hui.
He also warned them not to try anything funny or "he would gas the entire house with LPG and light it up so that they would all die together", said APP Lim.
Lay then stabbed the 27-year-old tenant in her neck, before pointing the knife at her friends and saying: "Don't think I don't dare to do it."
Shortly after, Lay's 59-year-old uncle took the knife off him. Lay's mother had called the uncle over.
Lay was taken to hospital with multiple stab wounds to his neck and eight stab wounds to his chest. The wounds were stitched up.
His victim was also taken to hospital. She had a life-threatening 1.5cm stab wound on the left side of her neck. She was initially given 33 days of medical leave and, later, another 59 days of medical leave.
She cannot carry heavy objects with her left hand for long periods and now does administrative work.
The maximum penalty for causing grievous hurt with a deadly weapon is life imprisonment, or up to 15 years' jail with a fine or caning; and for criminal intimidation, where the threat is to cause death, up to 10 years' jail and a fine.
Correction Note: In an earlier version of this story, Lay Chee Leong's name was misspelt. We are sorry for the error.