He saw an image of his colleague flying in from his kitchen window and telling him that she wanted him to die.
Pua Kok Heng, 57, who had just been fired from his cleaner job the day before, got angry.
He had been dismissed after threatening his colleague, Madam Goh Ah Moy, 62, with a knife.
Pua then tucked two knives into his waistband and headed to Jurong East MRT Station to look for Madam Goh.
When he found her, he stabbed her in the chest.
She died at the National University Hospital about an hour later.
Pua, who suffers from paranoid schizophrenia, yesterday pleaded guilty to culpable homicide on Nov 24, 2011.
Two days before the fatal attack, when he was still working as a cleaner at the MRT station, Pua used Madam Goh's equipment to clean the plant rooms.
She later scolded him for dirtying her mops and pails, and they had a heated argument.
Pua's colleague, Mr Rodney Tan Kim Khuay, 70, intervened before the matter got out of hand.
Mr Tan was also Pua's flatmate.
At home the next day, on Nov 23, 2011, Pua had a hallucination of Madam Goh floating into his rental flat in Marsiling.
The apparition "challenged" him to go to Jurong East MRT Station with a knife.
Pua took a knife and went to the MRT station.
At 8.30am, his supervisor, Mr Simon Lim Kim Heng, saw Pua shouting and hurling vulgarities at Madam Goh in the public concourse area.
She appeared stunned and was rooted to the ground.
When Mr Lim asked Pua to calm down, he told his supervisor not to interfere and took out the knife.
Shocked, Mr Lim fired him on the spot, but this did not deter Pua from approaching Madam Goh.
Mr Lim shouted at her to run away but she remained immobilised. He shouted at her again and this time, she complied.
Mr Lim accompanied Madam Goh to the ground floor of the MRT station. He then informed the duty station manager and his company's manager about the incident but no police report was made.
The next day, Pua had another hallucination of Madam Goh.
This time, she was taunting him in Hokkien.
Angered by this, he took two knives from his flat, took public transport to the MRT station and fatally stabbed Madam Goh at about 2.25pm.
Pua stood beside her and waited till Madam Goh stopped moving before he left.
A passer-by saw her lying on the floor near the station's bicycle bay and called the police. Pua was arrested that evening.
Urging the court to give Pua a life sentence, Deputy Public Prosecutor (DPP) Jasmine Chin-Sabado said he needs long-term psychiatric treatment, preferably in a confined setting like a prison.
She also stressed that the stabbing occurred at a public place and Pua also had delusions about killing Mr Lim.
Pua's lawyer Josephus Tan asked Justice Lee Seiu Kin to sentence his client to not more than 20 years in jail.
Justice Lee will sentence Pua at a later date.
For culpable homicide not amounting to murder, he can be jailed for life or up to 20 years and fined. He will not be caned as he is above 50 years old.
This article was published on April 18 in The New Paper.Get The New Paper for more stories.