The Voluntary Euthanasia Party's South Australian Senate candidate at last year's election has died in an Adelaide motel room after taking the lethal drug Nembutal.

Max Bromson, 66, had been terminally ill with bone cancer.

Euthanasia advocate Philip Nitschke says Mr Bromson bought Chinese Nembutal after joining the Exit International "buyer's club".

Mr Bromson drank the drug on Sunday night, surrounded by family.

"He died in peace, it was very quick, very peaceful," Mr Bromson's sister Kerry said.

"And it's a horrible thing to say, but it was lovely in a way because we could be with him."

Mr Bromson had left a note and filmed his own death to prove his family did not assist him.

"To do it yourself will require strength and commitment, which is fine," Mr Bromson had previously told the ABC.

"I have my head around that, that's because there isn't a legal alternative."

His phone message left no doubt as to his intentions: "Hello, this is Max Bromson. I am deceased as of July 27, please do not leave a message."

Family's mobile phones and computers confiscated

Dr Nitschke said Mr Bromson's family informed police on Monday morning of his death and was told an inquest would be held, despite the note and video.

Family members had their mobile phones, tablets and computers seized by police and were told it could be up to two years before they would get them back.

Ms Bromson said it was a waste of police resources.

"We had 17 police, now a coroner's inquiry - where the man left a note," she said.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 6 minutes 31 seconds 6 m Nitschke says medical board suspension is politically motivated

"It's documented. He didn't want to be here."

Dr Nitschke said Mr Bromson was "a person who knew what he wanted".

"He needed a degree of information, which he got, and he needed some assistance in some ways, such as the testing of drugs and all that," he said.

"It will be interesting to see how far they push this one."

The Nembutal used by Mr Bromson was tested for its purity at Dr Nitschke's Adelaide clinic.

Dr Nitschke's registration was suspended last week over his involvement with a Perth man, who took his own life but was not terminally ill.

Police will now question him about Mr Bromson.

South Australia Police says its Major Crime Unit is investigating to see if the criminal offence of assisting in a suicide has been committed, and released the following statement:

South Australia Police is aware of the claims made on Dr Phillip Nitschke's website related to the death of a man earlier this week. Major Crime Investigation Branch is now conducting further investigation and a full assessment of the facts in order to determine whether any criminal offences have been committed. The response by police has been consistent with any investigation into a death that may have resulted from a criminal act. Usual protocols have been followed, with the scene properly examined and items seized that may provide evidence. Interviews were conducted and statements taken. To comply with our obligation under the law, those present were cautioned as they may have been committing a criminal offence of assisting in a suicide. The investigation remains ongoing.

People seeking support and information about suicide can contact Lifeline on 13 11 14.