A Queensland police officer told a Crown investigation that the lack of resources explains why her colleagues ignored an email asking for mental health support from Joel Cauchi, who killed six people in Sydney’s Bondi junction in one year.

Monday's investigation heard an officer was the police's sole mental health official when he received an email from another officer, and the area served 220,000 residents, asking him to follow up with the Cauchi family.

Cauchi confiscated the knife amid his father's concerns about his son's mental health, and after his father confiscated the knife, he called police officers to his parents' home in Toowoomba.

Cauchi's mother told police: "Unless he does something violent, I don't know how we're going to get his treatment."

On Tuesday, when asked about her colleagues who had held the position for five weeks and missed emails, they were often officials of mental health officials.

"His oversight over (that email) is devastating and does not indicate that he is an official or how he plays my role," she told the court.

The survey was planned to stab six people at Westfield Bondi junction in April 2024, and the investigation was studied.

Cauchi, 40, killed Ashlee Good, 38, Jade Young, 47, Jade Young, 27, Pikria Darchia, 55, Dawn Singleton, 25, and Faraz Tahir, 30, and was shot and killed by police inspector Amy Scott on April 13 last year and was injured in a shopping mall on April 13, 10.

The investigation heard Tuesday that police responses to Queensland's mental health calls grew by more than 50% between 2016 and 2020, but police were not equipped with "skills and knowledge" to respond.

Officials responsible for mental health interventions in the Darling Downs area where their parents live in Cauchi said her stance is quickly becoming an overwhelming role”.

“On any day, I can receive 30 to 40 emails,” she told the court when referring to other officials’ requests for mental health events.

The court heard she was unable to find another official to answer her role when she provided evidence in the investigation at the Lidcombe Coroner's Court this week.

She was scheduled to take three weeks off soon, but only one backfilling was a week.

The court heard that when an email was sent to ask Cauchi for follow-up measures, she would go to work at work and she would call or meet with the Cauchi family to discuss their choices.

She told the court that she would have searched Cauchi's history in the police database and found that he had three interactions with the police for an unstable driving.

The court heard she would know that in July 2022, Cauchi repeatedly called a boarding school to ask if she could watch female students perform sports activities.

In 2021, police reported that he screamed and said he was diagnosed with schizophrenia and took medication.

The official told the court that part of her follow-up will include contacting her Queensland Health peers “immediately” to learn about their relationship with Cauchi.