AN evil woman who butchered a four-year old boy before killing his grandmother with gardening shears was arrested before she could murder the boy’s mother.

Chinese national Cai Xia Liao bragged that she had killed everyone her former lover had loved and would murder his daughter before police intervened.

The 45-year old, who was in Australia on a tourist visa, has pleaded guilty to two counts of murder and related charges over the terrifying attack in March.

Giangwa “Brian” Mach lay helplessly bound in his Albanvale home as Liao murdered his family in a sickening act of revenge.

“I’ve killed everyone to make you suffer and if I’m happy I’ll let you go with them,’’ she told him.

Mr Mach met the deranged Liao, who wanted Australian citizenship, while separated from his wife.

He met Liao through a friend while estranged from his wife and holidaying in China.

The pair struck up a long distance relationship and would catch up with each other in their respective countries.

But when Mr Mach declared he still loved his wife, things quickly turned sour.

And when he tried to break off the relationship, Liao threatened to kill his wife Mai.

On the morning of March 31, she carried out her murderous plot, drugging Mr Mach and murdering his beloved grandson Alistair Kwong, whom he was babysitting for his daughter.

When Mr Mach gained consciousness, he was forced to listen as his wife was slain outside after returning home from work.

He heard the 60-year-old grandmother cry out repeatedly for help before she was silenced.

Court documents have revealed Liao was caught in the act of her murderous rampage by a worried neighbour, who took photos of the attack.

The neighbour climbed onto his roof and snapped Liao standing over Mrs Mach, who was lying on the concrete with her hands up in a defensive position.

Court documents state Liao then returned with the bloody shears to brag about her murderous exploits.

“I used these, I cut the b---h’s throat,’’ she told Mr Mach.

Liao then told Mr Mach she planned to wait for his daughter to pick-up her son and kill her too.

She was arrested before she could fulfil her murderous plan.

Liao apologised to the family of her victims today through her lawyer David Gibson.

“Ms Liao wishes to apologise to the family for the terrible grief her actions have caused them,” he said.

Liao had lay in wait for her victim for nine hours while Mr Mach lay bound and gagged inside his home.

Alistair was fatally stabbed 18 times in his head and neck while he lay in bed.

Documents state Mr Mach had shared a special bond with the little boy and cried out frantically for him on gaining consciousness.

But Liao refused to provide answers, instead kicking him in the head, face and chest throughout the afternoon.

“What time that b---h coming home,” she said.

At one point she smashed the shears across his head and pointed them toward his eye.

When his wife arrived home at about 5pm, she was attacked without hesitation.

Post mortem examinations have revealed Mrs Mach suffered more than 23 stab and slash-type wounds.

Police found Liao sitting on the couch next to Mr Mach.

When paramedics cut off his gag, the first thing he did was ask about his grandson.

Liao made no comment when interviewed.

She will reappear in the Supreme Court tomorrow.

wayne.flower@news.com.au