An inquiry has been ordered into the care of a "delusional" murderer who was considered for sectioning shortly before killing a woman with a bolt gun.
Mary Griffiths, 38, of Bury St Edmunds, Suffolk, died early on 6 May 2009 after the attack, which also left one of her three daughters with minor injuries.
John McFarlane, 40, was jailed for life for the murder in November 2009.
The BBC revealed in May 2009 that shortly before the attack McFarlane was treated at West Suffolk Hospital.
It is believed medical staff at the hospital asked the authorities to look at whether he should be held under the mental health act, but it was decided not to detain him.
Dragged from room
The Suffolk Mental Health Partnership NHS Trust conducted an internal inquiry which was passed to NHS East of England (NHS EoE) - which has now ordered an independent investigation.
A spokeswoman said: "NHS East of England has commissioned an independent company to undertake an independent investigation into the care and treatment of John McFarlane.
"The investigation is now under way and a report detailing its findings will be published once the investigation is completed."
A person can only be detained if independent mental health professionals find he is a danger to others, or in some circumstances him or herself, and that detention would be the best option.
The Independent Police Complaints Commission (IPCC) is also investigating the case after it was revealed that Ms Griffiths had called the police before the stabbing to complain of being harassed by a man.
McFarlane, who worked as a slaughterman at the nearby Denham estate, took revenge after fitness instructor Ms Griffiths posted a Facebook message saying he was "delusional" if he thought they would ever have a relationship.
He smashed through the back door of her home with an axe as she and her three daughters slept.
McFarlane dragged Ms Griffiths from the room, where she had been sleeping with her 10-year-old daughter, and beat her.
She was shot twice in the chest and once in the left shoulder with a bolt gun normally used for stunning livestock.