Angry at his wife who refused him money to fuel his drug habit, a man in Pulau Gaya, Sabah, slashed her multiple times with a cleaver before setting her on fire, reported Harian Metro.
The 30-year-old man fisherman also slashed the couple's adopted son.
In the incident three days ago, the man approached his wife Darwina Tatuh, 54, at their stilt house in Kg Pondo, Pulau Gaya, for money to buy syabu.
Darwina refused, leading to a fight between the two.
The man then slashed his wife several times with a cleaver, splashed petrol on her and burned her alive.
On realising that their adopted son Randi, six, had seen the violence, the man used the same cleaver on the child, resulting in severe injuries to the neck and back and his left wrist was nearly severed.
Darwina's body was sent to the Queen Elizabeth Hospital for a post-mortem, while Randi was rushed to the Likas Hospital, where he was reported to be in stable condition.
Villagers caught the suspect and turned him in at the Kota Kinabalu marine police base.