Aboriginal academic and activist Gracelyn Smallwood wants answers over the death of her nephew, Lyji Vaggs. Credit: The Courier-Mail

Debbie Lampton, mother of the mentally ill man who died after being handcuffed by police and injected with anti-psychotic drugs at the Townsville Hospital speaks out about the harrowing ordeal.

On Wednesday, her sone Lyji Vaggs went to the mental health unit seeking help, but was told to go home. He was restrained and sedated after becoming aggressive towards hospital staff, and then stopped breathing.

The father of three was soon revived after 40 minutes and admitted into intensive care unit in a critical condition, until his life support was switched off.

New Ltd was told by Mrs Lampton that she was the last to leave his bedside after reciting a prayer before turning off the life support system.

Mr Vaggs had been receiving treatment for bipolar and schizophrenia at the hospital for the past two years but was told that tragic day as well as the Tuesday before that no beds were available.

The family are awaiting results of the post-mortem and will consult with their lawyers to analyze their alternatives.

Mr Vagg's aunty and Indigenous activist Gracelyn Smallwood supported calls from the Queensland Greens for a full investigation into how police and corrective services deal with Indigenous residents.

''There have been more deaths in custody since the Royal Commission into Aboriginal Youth and there has been a lack of implementation from all government departments and services to improve outcomes for indigenous Australians across the board - education, health and social justice,'' she said.

''If the Prime Minister is talking about closing the gap then we need to start fresh.