A 70-year-old man and his 27-year-old daughter were found dead at Block 560, Pasir Ris Street 51 on Sunday afternoon (Aug 20).
The police, who were alerted to a case of unnatural death at 1.30pm, said they found the man lying motionless at the foot of the block.
Upon further investigation, the woman was found in the same state in a residential unit on the second floor.
"Both were pronounced dead by paramedics at the scene. Police investigations are ongoing," said a police spokesman.
According to Shin Min Daily News, the woman, who was the man's youngest daughter, had multiple slash wounds on her body, including one on her neck.
She had special needs and was a student at the Movement for the Intellectually Disabled of Singapore, reported Lianhe Wanbao. Her father appeared to be her main caregiver.
A neighbour told reporters that the father doted on his daughter and would often take her downstairs for a stroll.
He added: "She walked slower than her father, but he would stop and wait for her. It was clear that she was dependent on him."
The New Paper reported that a woman in her 70s, believed to be the man's wife, was seen wailing at the scene.
They have another daughter, who is married, a son, as well as two grandchildren. All of them, including the two victims, lived together.
A resident, who lives two doors away from the family, told The Straits Times that he heard a loud sound and thought someone had thrown furniture down the block.
Mr Azman, 58, said: "He was already lying on the floor... I thought why this man was lying on the ground... he had a big cut on his right leg [from the knee to the shin]. At first, I thought maybe he was drunk or had fainted.