Calocane stabbed to death Barnaby Webber, Grace O'Malley-Kumar and Ian Coates in Nottingham in June, and tried to kill three others with a van.

He was sentenced to detention in a high-security hospital after prosecutors accepted his manslaughter plea rather than pursuing a murder conviction.

The deal was done as experts agreed he had paranoid schizophrenia so wasn't fully responsible for his actions.

The victims' families have criticised the sentence - as well as authorities they say could have prevented the tragedy.

Speaking at court on Thursday, Mr Webber's mother Emma said "true justice has not been served" and accused a police chief of having "blood on your hands".

"This man [Calocane] made a mockery of the system and he has got away with murder," added Mr Coates' son James.

A spokesman for attorney general Victoria Prentis, the government's chief lawyer, confirmed a referral had been received on Thursday.

She now has 28 days to decide whether to refer the case to the Court of Appeal for judges to decide if the sentence is appropriate.

However, it's understood the attorney general is unlikely to look at whether the correct charge was pursued.

It's not known who made the referral, but any person or institution can ask for a review.

Labour leader Sir Keir Starmer said it "probably makes sense" for the attorney general to send the case for review and to "have it double checked by the Court of Appeal", telling ITV's This Morning: "The family are entitled to have a review and the Court of Appeal to look at it."

He also backed calls for an inquiry into any failings within the police, health and court bodies that could have led to the attacks, saying it was "the least that these families are owed".

The former head of public prosecutions added: "I am very worried by what appear to be a number of points at which action could have been taken that would have prevented this happening.

"The family are saying that needs to be an inquiry into that. I think they're right about that. I think somebody outside of this independent needs to look at exactly what happened, what were the points of which there could have been an intervention and why it didn't happen."

Asked if Rishi Sunak backed calls for an inquiry, the prime minister's official spokesperson resisted, saying: "We believe that it's important that as the first action that the relevant agencies look back and ensure that all the proper processes were followed and that reasonable steps that could have been taken were taken to ensure that where there are lessons to be learned we do so."

However, they did not rule out an inquiry at a future date, adding: "We think that it's right that what happens now is that the relevant agencies look back. We're going to let that process take place."

The sentencing judge, Mr Justice Turner, said 32-year-old Colocane would "very probably" be detained in a high-security hospital for the rest of his life.

Families were united outside court as they accused the Crown Prosecution Service, police and the NHS of multiple failures.

They said prosecutors had already made up their minds when they informed them they would accept Calocane's manslaughter plea.

"At no point during the previous five-and-a-half-months were we given any indication that this could conclude in anything other than murder," said Mrs Webber.

'He knew it was wrong'

She said although Calocane was mentally unwell, the attacks were premeditated and "he knew entirely that it was wrong but he did it anyway".

Nottingham Crown Court heard he had previously been detained in hospital four times under mental health laws and had a history of refusing his medication.

Calocane was also arrested for assaulting a police officer in September 2021, involved in criminal damage and once visited MI5 headquarters to ask them to stop "controlling him".

Rob Griffin, Nottinghamshire Police's assistant chief constable, admitted "we should have done more to arrest him" after he failed to appear in court for assaulting the officer.

However, he said it was unlikely Calocane would have been jailed and there wasn't anything "obvious" to suggest he would commit the savage attacks.

Calocane's arrest warrant was still outstanding at the time of the killings.

Students Barnaby Webber and Grace O'Malley-Kumar, both 19, died after being stabbed repeatedly as they walked home in the early hours of 13 June.

Grace tried to save her friend but was also attacked.

Calocane walked away calmly and later stabbed school caretaker Ian Coates 15 times, stealing the 65-year-old's van and using it to knock over three people.

Calocane admitted attempted murder over the van attack.

Police tasered him soon after and found two knives and a scaffolding pole in his backpack.

The court heard Calocane would hear voices telling him to kill people or his family would be hurt. However, he wasn't taking his prescribed medication.

Prime Minister Rishi Sunak has declined to back calls for a public inquiry into alleged failings.

However, he said it was "important that all the relevant agencies look back to ensure all reasonable steps that could have been taken were taken and if there are any lessons to be learned that we do so".