The NHS Trust at the centre of the Don Lock killing has apologised to his family saying it "got things wrong".
Sussex Partnership NHS Foundation Trust also promised to review 10 cases where its patients had been involved in killings over the last five years.
Mr Lock, who had just got the all clear from prostate cancer, was stabbed 39 times in a road rage attack by paranoid schizophrenic Matthew Daley last July.
Daley was cleared of the 79-year-old's murder but found guilty of manslaughter on the grounds of diminished responsibility.
The Trust's chief executive Colm Donaghy has apologised to the Lock family and admitted it was "too little, too late".
Asked if the killing could have been avoided had Daley been diagnosed differently, Mr Donaghy said: "We cannot say that out of absolute certainty or any high degree of certainty.
"On behalf of the Trust, I apologise unreservedly because the care we provided to Matthew Daley should have been better.
"I also want to offer my sincere condolences to the family of Don Lock and everyone else affected by this tragic, devastating incident."
History of mental illness
Daley had mental health issues for 10 years before the killing which got worse following the break-up of his parent's marriage.
He was referred to the Trust's services in 2008 where he received treatment from the early intervention service which helps people who are starting to experience psychosis.
He was later transferred to the care of community mental health teams where he received treatment for a combination of Asperger's syndrome and psychosis.
But experts called by the defence said Daley had been wrongly diagnosed with Asperger's and had had paranoid schizophrenia for years.
Plea for him to be sectioned
Daley's sister Rebecca described Mr Lock's killing as "everything we feared would happen over the last 10 years".
The court heard his family had pleaded with experts to section him for fear he would harm someone unless he got help with his "obsessional behaviour and the voices".
Mr Daley told jurors: "I am thinking to myself, this poor man and his family will have to live with my son's actions for the rest of their lives.
"They will never be able to understand what happened, their lives have been ruined, my son's life and expectations have been ruined, and it didn't have to happen."
'Dad would still be here if the NHS had done their job'
The family of Mr Lock said he would still be here if it were not for NHS failings.
Mr Lock's son Andrew said the manslaughter verdict had brought to a close "the most horrific 10 months of our lives and brings some sort of justice for dad".
He added: "It effectively provides the Daley family with what they wanted - their son in a safe place away from harm's way being treated correctly.
"For them they can still visit their son, hug him and talk to him... for us, all we can do is cling on to the wonderful memories of dad.
"Nothing we say or do now will bring dad back to us...it is clear that this incident confirms nothing more than that dad was simply in the wrong place at the wrong time."
Trust: 'We got things wrong'
The Trust's report could be completed by the end of the summer and will be published in full.
The Trust has recently introduced a digital system where patients and their carers can sign off on their care plan and family evidence can be recorded.