The families of the victims of Valdo Calocane have said services caring for him in the lead-up to the attacks "have blood on their hands", after it emerged a mental health trust "minimised or omitted" key details of the serious risk he posed to others.
The final part of a Care Quality Commission (CQC) review into the care of Calocane by Nottinghamshire Healthcare NHS Foundation Trust (NHFT) found risk assessments played down the fact he was refusing to take his medication and was having ongoing and persistent symptoms of psychosis.
It also questions how well the trust engaged with Calocane's family, who raised concerns about his mental state.
The victims' families said the CQC report "demonstrates gross, systematic failures" and also claim they have had confirmation that a public inquiry into the case will take place.
The special review of mental health services at NHFT was ordered by then health secretary Victoria Atkins in January after Calocane was sentenced to an indefinite hospital order.
The CQC said Calocane's records make it "clear" that he was "acutely unwell" throughout the two years he was under the care of NHFT.
He was psychotic and suffering from paranoid delusions before eventually being diagnosed with paranoid schizophrenia in July 2020.
Between May 2020 and February 2022, eight risk assessments were completed for Calocane by the trust, which the CQC said appear to have been carried out for each of his admissions to hospital and updated at other times during his care.
The regulator said that while some risks were highlighted, other assessments "minimised or omitted key details".
These include the fact Calocane refused to take his medication, had ongoing and persistent symptoms of psychosis, was violent to others when psychosis was not managed well, and escalated his violent behaviour in the later stages of his care.
Chris Dzikiti, interim chief inspector of healthcare at the CQC, said: "This review identifies points where poor decision-making, omissions and errors of judgments contributed to a situation where a patient with very serious mental health issues did not receive the support and follow-up he needed.
"While it is not possible to say that the devastating events of June 13 2023 would not have taken place had Valdo Calocane received that support, what is clear is that the risk he presented to the public was not managed well and that opportunities to mitigate that risk were missed."
The CQC said Calocane had "little understanding or acceptance of his condition" which could "have significantly impaired his ability" to weigh up the pros and cons of antipsychotic treatment and the risks of discontinuing it.
It would have been possible to treat him under section 3 of the Mental Health Act (MHA) 1983 - which would have given doctors the power to administer drugs against his will - on his fourth admission to hospital in January 2022, the regulator said.
Instead, he was treated under section 2 of the act, which is usually for patients who are not known to mental health services.
A statement from the families of Barnaby Webber, Grace O'Malley-Kumar and Ian Coates, said: "This report demonstrates gross, systematic failures in the mental health trust in their dealings with Calocane, from beginning to end.
"Clinicians involved at every stage of Calocane's care must bear a heavy burden of responsibility for their failures and poor decision-making.
"Sadly, this is the first of what we expect to be a series of damning reports concerning failures by public bodies in the lead up to the killings of our loved ones, and beyond.
"We were failed by multiple organisations pre and post June 13 2023."
The CQC report also questioned how well the trust engaged with Calocane's family and how well his discharge was planned.
It comes after his mother Celeste and brother Elias told the BBC's Panorama programme a psychiatrist warned Calocane could "end up killing someone" three years before the attacks.
Among its recommendations, the CQC said NHFT should review treatment plans for people with schizophrenia regularly, as well as ensuring clinical supervision of decisions to detain people under section 2 and 3 of the Mental Health Act.
It also called for NHS England to publish guidance setting out national standards for care for people with complex psychosis and paranoid schizophrenia in the next 12 months.
Health Secretary Wes Streeting, said: "I want to assure myself and the country that the failures identified in Nottinghamshire are not being repeated elsewhere.
"I expect the findings and recommendations in this report to be considered and applied throughout the country so that other families do not experience the unimaginable pain that Barnaby, Grace and Ian's family are living with."
The handling of the Calocane case prompted outcry and led to numerous inquiries into the public bodies involved, including Nottinghamshire Police and Leicestershire Police.
The victims' families added: "Along with the Leicestershire and Nottinghamshire police forces, these departments and individual professionals have blood on their hands.
"Alarmingly, there seems to be little or no accountability amongst the senior management team within the mental health trust. We question how and why these people are still in position."
A Nottinghamshire Healthcare NHS Foundation Trust spokesperson said: "We acknowledge and accept the conclusions of this report and have significantly improved processes and standards since the review was carried out."
Claire Murdoch, national director for mental health at NHS England, said: "The CQC have identified unacceptable failings in the care and treatment provided to Valdo Calocane.
"Nationally, the NHS has already started work to enact all of the CQC's recommendations, with every provider of mental health services reviewing the care that people with serious mental illness receive."
Marjorie Wallace, chief executive of mental health charity Sane, said: "This is the most damning indictment of the fact that psychiatric services are not in crisis but in complete breakdown.
"The rights of patients override those of the families, carers and public. How can it be that a highly disturbed patient with his history of sections and incidents of violence could choose not to engage with services and disappear into the community?
"The finding that truly concerns us is that, despite years of inquiries, families and carers with concerns about patients' deteriorating mental health have been ignored."
