A man murdered with a steak knife by a man released from jail four months earlier was "let down by the system", a police and crime commissioner said.
Declan Gray, 21, of Nuneaton, pleaded guilty last year to murdering Morgan Hehir in a park in the town.
Mr Hehir's father Colin called for a review into the supervision of Gray, who had served time for manslaughter.
Warwickshire PCC Philip Seccombe said he would "look into the circumstances which led up to Morgan's death".
Under current guidelines, Gray was released without supervision because he served his full sentence.
He had been arrested but not charged three times in the four months before killing Morgan Hehir, including twice on suspicion of wounding.
Colin Hehir put his concerns to Mr Seccombe and Warwickshire Police in a "productive" meeting.
"I believe Morgan's death was preventable with some form of police intervention," he said.
Declan Gray's brother Karlton Gray, 19, and Simon Rowbotham, 40, admitted manslaughter and were also jailed.
The defendants, from Nuneaton, had shouted abuse at Mr Hehir before an altercation broke out, police said.
Judge Richard Griffith-Jones said it had been a "ferocious and concerted cowardly attack" on Mr Hehir.
Mr Seccombe said he was "not blaming police" but that Mr Hehir's family had been let down.
He questioned whether processes for monitoring violent offenders after they had served their full terms of imprisonment were adequate.
Mr Hehir, who often visits Pool Bank Recreational Park, where his son was killed, said: "It's the place where Morgan took his last steps on that night.
"It does fill me with anxiety and dread to walk through here, but I feel the need to come here. You know, I can't stay away."