A 27-year-old man was arrested on suspicion of murder and arson after allegedly attacking his mother early yesterday, then setting fire to their Yuen Long home.
The body of the woman, 53, was found after the fire was put out. Police said she was attacked in her first-floor unit in Block 14 of the Long Bin Interim Housing Estate before it was set alight.
Firefighters and police were called at about 1.15am yesterday to put out the blaze in the 20 square metre unit, where the mother and son were said to have lived together for several years.
As they worked to extinguish the fire, the man could be seen perched on an air conditioner mounted outside the unit.
Witnesses said the man appeared to be in an agitated state, shouting "I love Jesus" as he jumped about six metres to the ground. His legs were broken in the fall and he was sent to Pok Oi Hospital, then transferred to Tuen Mun Hospital.
The blaze was extinguished in about 20 minutes. The woman's body was found beside a bed.
Yuen Long police chief inspector Chan Ka-po said: "It seems the son and mother were arguing before the fire started. We don't yet know the reason or what they were arguing about."
Chan said the woman's body was too badly burnt to conclude whether she had sustained other injuries. An autopsy will determine the cause of her death.
Flammable liquid and a lighter were found in the unit, and two knives were found on the ground outside the block, he said.
The man had recently lost his job at a cafe, according to neighbours. They said he often argued with his mother and had not been seen for several days before the incident. He did not have a history of mental illness.
Fifty people were evacuated when the fire broke out.
The estate was built in 1999 to provide temporary housing for people affected by government clearances or redevelopment. It is notorious for its poor conditions and problems with crime. Ninety-nine thefts were reported there in the first three months of last year alone. It has eight low-rise blocks with a total of 840 units, and 500 households. The Housing Authority plans to clear the estate in early 2016 to make way for public housing.