The sister of tragic Alan Geddes - stabbed 40 times by a homeless man– is calling for tighter controls on the release of violent and mentally-ill criminals.
Sandra Geddes, 65, says other families need protecting.
She called for an inquiry launched after the tragedy to deliver some clarity for her and her brother's family, as the Crown Office confirmed it will now look into Stuart Quinn's offending history as part of its investigation.
Alan Geddes was stabbed 40 times by homeless Quinn after he gave him a place to stay in December 2019.
Quinn had been released from HMP Grampian in Peterhead and travelled to Aberdeen to find his temporary accommodation closed.
Ms Geddes said she believes her brother would "still be alive today" if the ex-con's previous convictions and psychopathic behaviour had been properly assessed - as he may never have then been released.
The Crown Office said these aspects will now form part of its investigation.
Mr Geddes, who was described as a "devoted dad", allowed Quinn to stay the night in his flat in the city's Ruthrieston Crescent.
The 35-year-old was sentenced to a minimum of 18 years for the killing at Glasgow's High Court last month.
Ms Geddes said she believes "something went very wrong", not only in relation to Quinn's release, but equally in how the nature of his previous convictions and paranoid hallucinations were handled by authorities.
She also wants answers for Mr Geddes' eight-year old son, Lucas.
"My first thoughts when I heard about Alan's death were for his son, Lucas - he adored his dad," Ms Geddes said.
"Alan went out that night telling Lucas he'd see him in the morning, and for his mum Lisa to have to tell him his dad isn't coming back must've been absolutely horrendous for a mother to have to tell a little boy.
"I don't want this to define his life and I hope, with me trying to get the answers here, it might help a little bit when he gets older - I can actually explain what happened and why it happened."
Quinn, a former offshore worker, had a catalogue of convictions for violent offending before he murdered 56-year-old Mr Geddes, including holding one girl hostage for more than two hours.
A month later, he attacked another neighbour with a screwdriver.
Ms Geddes also believes Quinn was let down by the justice system, which ultimately led to the death of her brother.
She said: "I'm not an expert, but with all the issues Stuart Quinn has had up to the murder of my brother, that would have rung alarm bells to me that this guy has got serious, serious problems - and I often wonder if he was crying out for help and didn't get it.
"I need to find out where this went wrong and even try to make it a law that prisoners with serious mental health problems can't be released without somewhere to go, that they don't just go from being in jail to on the street.
"I don't think that's where we want to go as a society because more people will die because the system failed.
"I believe, if the system had done its job, my brother would still be alive today.
"But if it hadn't been my brother, it would have been someone else, because it was inevitable Quinn was going to kill someone.
"I don't want another family to have to live with the heartbreak that we've had."
Earlier this month, Ms Geddes met with justice minister Humza Yousaf to voice her concerns and call for an investigation into the circumstances around her brother's death.
It is now being probed by the Crown Office Scottish Fatalities Investigation Unit.
Ms Geddes said she is "apprehensive" about the outcome of the investigation, but added that she got a "good response" from Mr Yousaf.
She said: "The investigation is focusing on his release but I also want to know why Quinn wasn't picked up prior to that - that's a huge part of it.
"If he'd been assessed properly back in 2018 they surely would have seen he was psychotic. I think there are a lot of things that need to be looked at.
"Was he on medication? Was the prison low on staff? Was it a mistake? I don't know.
"And that's why the investigation has to look into these things because these things can't continue to happen."
A spokeswoman for the Crown Office and Procurator Fiscal Service said: "The investigation into circumstances surrounding the death of Alan Geddes, under the direction of the Scottish Fatalities Investigation Unit (SFIU), is ongoing and the family will continue to be kept updated in relation to any significant developments."
A Scottish Government spokeswoman added: "Our thoughts and sympathies are with Mr Geddes' family and the justice secretary was grateful for the opportunity to meet with Sandra Geddes and listen to her concerns about this case.
"It would not be appropriate to comment further at the present time."
