Parents mourn 'very sick boy' after Sydney stabbing rampage

To some, Joel Cauchi is a "monster".

But his devastated father has described the man behind a deadly Sydney shopping centre rampage as a "very sick boy" who let himself down.

Andrew Cauchi said he'd done everything in his power to help his "beautiful" son who lived with mental health issues for decades.

"I'm loving a monster. To you he's a monster but to me he was a very sick boy," he told reporters on Monday.

Cauchi's estranged family expressed their devastation and sorrow for the six people killed in the mass stabbing event at Westfield Bondi Junction.

His parents were still trying to comprehend what happened when they spoke directly to media outside their Toowoomba home west of Brisbane.

"I'm extremely sorry, I'm heartbroken for you," Mr Cauchi said to victims' families.

"This is so horrendous I can't even explain it. I'm just devastated, I love my son."

Mr Cauchi said they had done what they could to take care of their son before he went off his medication and "took off" to Brisbane.

Cauchi made periodic contact with his family, moving to Sydney from Queensland in March.

His family contacted authorities after seeing his image in TV reports about the weekend attack.

"I made myself a servant to my son when I found out he had a mental illness, I became his servant because I loved that boy," Mr Cauchi said.

"You don't know how beautiful this boy was ... I did everything in my power to help my son.

"He let himself down. He was taken off medication because he was doing so well but then he took off to Brisbane."

Cauchi, 40, targeted women in the attack.

The rampage ended when he was shot dead by police inspector Amy Scott who confronted him at the shopping centre.

Cauchi's mother Michele did not know what motivated her son's attack, saying he was "brought up in love".

He asked for his medication to be reduced over a number of years before leaving the family home, she said.

"This is a parent's absolute nightmare when they have a child with mental illness, that something like this would happen," Mrs Cauchi said.

"And my heart goes out to the people my son has hurt. If he was in his right mind he would be absolutely devastated with what he has done.

"He was obviously not in his right mind. He was somehow triggered into psychosis and lost touch with reality."

Mrs Cauchi said her son had lots of friends growing up "until he got sick".

She urged people who had family members with mental health issues to seek support.

Flowers arrived at the Cauchi residence on Monday, with the parents expected to be visited by NSW detectives.

"We're just ordinary people who brought up our son as best we could," Mrs Cauchi said.

"I'm so sorry about what my son has done. We don't know why he did what he did - it was very out of character."

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