A woman will appear in court on Thursday accused of murdering a four-year-old boy and his grandmother with garden shears at a Melbourne home.



Chinese national Cai Xia Liao, 45, allegedly bound and gagged her former lover Brian Mach at his Albanvale home early on Tuesday morning before fatally stabbing his grandson Alistair Mach in the head and neck while he lay in bed.



She is accused of waiting at the property for 10 hours until Alistair’s grandmother Mai Mach, 60, got home from work, before attacking and killing her in the backyard.



Liao, who is in Australia on a tourist visa, will appear in the Melbourne magistrates court charged with two counts of murder and one count each of intentionally causing injury and false imprisonment.



She had been in a relationship with Mach, 61, for about three years but he recently called it off, Detective Leading Senior Constable Tony Harwood said.



He said Liao had showed up at Mach’s home about 6am on Tuesday – while he was babysitting his grandson Alistair and his wife was at work – and an argument erupted, police alleged.



“Brian was assaulted and subdued,” Harwood told an out-of-sessions court hearing on Wednesday.



“He’s been bound and gagged. The accused entered a bedroom where Alistair was in bed, while carrying a large pair of garden shears.”



Harwood alleged Liao stabbed Alistair as he lay in bed, causing severe head and neck injuries, with a postmortem examination revealing he had suffered more than 18 stab and slash wounds as well as defensive injuries.



Liao then allegedly waited for Mach to arrive home from work and continued to assault Mach, who was tied up in the living room.



Mach drove into the rear yard of her home and was confronted by Liao as she approached the door, Harwood said.



“Mai Mach was chased into the backyard by the accused and attacked with the same pair of garden shears, also suffering extreme neck and head injuries,” he said.

She suffered more than 23 stab and slash-type injuries, he said.

Harwood said the alleged killing had been witnessed by a neighbour, who called police.

Mach was taken to the Royal Melbourne Hospital with minor injuries, requiring heavy sedation.

Liao declined to comment during the out-of-sessions hearing, only telling the bail justice that she takes blood pressure medication.

Flowers and a toy have been placed outside the Mach’s Albanvale home.

Alistair, described as “bubbly” by family friends, was an only child.