Home Affairs Correspondent, BBC News, West
A Swindon man who strangled and battered his parents to death should never have been free in the community, his sister has said.
Timothy Crook was sentenced to an indefinite period in a secure hospital
Timothy Crook was mentally ill but staff from the Avon and Wiltshire Mental Health Trust failed to turn up and section him.
Four days later Elsie and Robert Crook were dead. A jury took just 45 minutes to find him responsible for killing them.
As a judge sent her brother to a secure hospital for an indefinite period, Janice Lawrence said the deaths could easily have been avoided.
For years, Ms Lawrence fought to protect her elderly parents as they were tormented by her brother.
She blames the Avon and Wiltshire Mental Health Trust for not taking sufficient action.
"I just cannot believe this has been allowed to happen. They knew of his background, they knew all the problems that had been happening, all the alarm bells sounding," she said.
"They knew the danger my parents were in, they knew what was going on and they still didn't act on them."
The BBC has seen a report of an internal investigation by the trust which reveals a series of errors.
In 1997 Timothy Crook joined the RAF - stationed at Lincoln and then at Lyneham - close to his parents' home.
But two years later he lost his job and returned to the family home in a fit of rage.
He punched and kicked his father, leaving his mother terrified. After that he went back to Lincoln and was taken to a secure unit.
But in 2002 he was released into the community. A year later he was back living with his parents and, crucially, stopped taking his medication.
For the next four years Ms Lawrence desperately tried to get his medical records transferred from Lincoln.
When they eventually arrived she pleaded for her brother to be sectioned. The local crisis team agreed to go to the family home, but they never turned up.
Instead she got a phone call.
Crook drove his dead parents to a house he owned in Lincoln
"I was rung and told that they'd discussed the case with a social worker and the social worker had decided that because this case had been going on for five years it wasn't actually urgent and there was no need to come out."
Two days later Mr and Mrs Crook were dead.
After strangling and beating them Crook stuffed their bodies into their car and drove to Lincoln, where he dumped them in the back garden of his house.
He was deemed to be too mentally ill to plead at his trial but the jury were in no doubt that he was responsible for Mr and Mrs Crook's deaths.
Sentencing him to an indefinite period in a secure hospital, Mr Justice Evans said he hoped the appropriate authorities had learned lessons from the case.
An independent external inquiry into the incident will now be carried out.
Ms Lawrence simply wants to know why it was allowed to happen.
In a statement Avon and Wiltshire NHS Trust said its thoughts were with the family and friends of Robert and Elsie Crook.
"Although Mr Timothy Crook was never formally under the care of Avon and Wiltshire Mental Health Partnership NHS Trust an internal investigation has taken place and we have met with the family to discuss the outcome.
"Since this tragic incident took place the trust has reviewed its procedures in order to ensure that the public can be assured of the highest standards of care from us.
"NHS East Midlands are currently in the process of commissioning an independent investigation to look into this case.
"This investigation will examine the care and treatment of Timothy Crook in both NHS East Midlands and NHS South West, following which, recommendations for improving practice will be made for both regions."