A woman accused of murdering a four-year-old boy and his grandmother with garden shears at a Melbourne home has appeared in court.

Chinese national Cai Xia Liao, 45, allegedly bound and gagged 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.

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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.

Alistair Mach. Source: Fairfax Media

In a brief appearance, Liao sobbed loudly and uncontrollably in the dock, in front the victims’ family and friends, who sat just metres away.

Her lawyer Sarah Pratt told the court Liao was having suicidal thoughts and it was her first time in custody.

The mother of four-year-old Alistair Mach sat holding a small teddy bear during the brief hearing, and was supported by a large group of friends and family.

Liao, who is in Australia on a tourist visa, was charged with two counts of murder and one count each of intentionally causing injury and false imprisonment.

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

He said Liao showed up at Mr Mach’s home about 6:00am on Tuesday – while he was babysitting his grandson Alistair and his wife was at work – and an argument erupted.

“Brian was assaulted and subdued,” Detective Senior Constable 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.”

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

Ms Mach drove into the rear yard of her home and was confronted by Liao as she approached the door, Detective Senior Constable 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, Detective Senior Constable Harwood said, as well as having defence wounds.

Detective Senior Constable Harwood said the alleged killing was witnessed by a neighbour, who called police.

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

Expressionless, 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.

ABC/AAP