The male suspect, 37, Siu, a clerk, was arrested in Ma On Shan yesterday. He had been detained for questioning as of today.

At 1 am on Friday, he broke into a first-floor unit in Heng Kong House of Heng On Estate in the same district.

The suspect then entered a bedroom, after which he smothered the female resident, Kwong, 36, falling asleep there with a pillow, clutched her neck and rammed her head against the wall.

Shortly afterwards, he fled the scene empty-handed in fear of the Kwong screaming for help.

Kwong, sustaining injuries to her face, neck, shoulder and arms, reported to the police and was sent to Prince of Wales Hospital in Sha Tin for treatment.

Later, police found no loss of valuables in Kwong’s unit but a lock, a stack of keys and a wide-angle viewer of the wooden door.

They also found an “X” written on the unit’s iron gate, suspecting it to be a symbol burglars used to mark out homes they want to target.

Sources said the suspect had been marking out apartments in Ma On Shan for targeting.

They also said the victim, a digital account executive, had been living alone in the involved unit after her family members had moved overseas.

She later recounted the whole incident on social media, saying she fell asleep past midnight after getting off work before the burglary happened.