A woman whose mentally ill son killed her father has called for more communication from NHS trusts.
William Barnard, 30, stabbed his grandfather John McGrath to death in July 2009.
Kathleen Barnard, from Nottingham, said the family were not told he had stopped taking his anti-psychotic medication after he was told the drug was voluntary.
Nottinghamshire NHS Healthcare Trust has apologised for its failings.
Ms Barnard said: "My dad would call the mental health team to let them know that he was worried.
"They never assessed the risk in him and they never monitored him."
Barnard also attacked his grandmother Mable McGrath, who was seriously hurt in the incident at the couple's home at Thorpe Close in Stapleford.
"He did have some crazy idea that my dad belonged to a cult," said Ms Barnard.
"He visited them and was going on about this cult in the morning. He returned that night, didn't speak, just knocked on the door and before my mum knew, he'd already stabbed my dad.
"My mum tried to pull him off and she got stabbed."
Ms Barnard said her son, who is back on his medication, cried when he was told what he had done.
"He couldn't believe he could do such a thing to people that he loved. He loved my dad dearly and my dad loved him."
She said the tragedy has brought her family closer together.
"The whole family knew that Will was ill and all we wanted to do was get him the help. My dad would still be fighting Will's corner if he was alive."
A report by the NHS trust into Barnard's care said there was "a disregard as to the significance of risk factors relating to Patient 09's [William Barnard's] deteriorating condition" and that his care "fell below acceptable standards".
A second inquiry is being carried out by the Strategic Health Authority.
Barnard, who inflicted 56 wounds on Mr McGrath, was committed to Rampton high security hospital indefinitely in June.
He admitted manslaughter on the grounds of diminished responsibility and pleaded guilty to a charge of wounding Mrs McGrath with intent.