The mother of an Auckland man allegedly killed by a mentally ill flatmate says the mental health system has "absolutely failed" her and her son.

Dean Clark, 36, was killed at his home in the suburb of Balmoral on Tuesday night.

His 38-year-old flatmate has been charged with murder and been granted interim name suppression.

He was remanded to a psychiatric hospital for assessments on whether he is fit to stand trial.

Mr Clark's mother, Adrienne Clark, told the Herald on Sunday the mental health system has let her down.

Her son had known his accused killer for 10 years but the man only moved in with Mr Clark a week before his death.

"The mental health system has absolutely failed. The laws need to change and become more stringent but this is not the time to talk about that," she said.

Mrs Clark said her son had a new partner and was training for a new job, and had a lot to look forward to.

In a statement, Auckland District Health Board says it is aware of a serious incident "involving a person known to our mental health services" and it would carry out an investigation.