Axel Rudakubana, who was 17 years old at the time of the events, showed “violence so extreme” that he is “difficult to understand” the attack, the judge said.
The body of the youngest girl, Bebe King, bore more than 120 knife marks.
Eight other children and two adults were injured.
“Broken”
“If he could, he would have killed every child and every adult in his path.”said the judge.
Axel Rudakubana pleaded guilty on Monday, cutting short the trial, initially scheduled to last four weeks.
He could not be sentenced to irreducible life imprisonment because he was a minor at the time of the attack.
Conservative opposition leader Kemi Badenoch called for a change to this law.
Southport MP Patrick Hurley said the sentence was “not harsh enough”. He took the matter to court so that it could be re-examined.
The latter has 28 days to decide whether or not to refer the conviction to the Court of Appeal.
Axel Rudakubana gave no explanation for his actions.
On Thursday, he had to be taken out of the dock twice because of his behavior. “I feel very bad, I need to see a doctor”he yelled, saying he hadn’t eaten in 10 days.
He did not attend the verdict.
Relatives of the victims were in tears in court where the prosecutor gave the horrifying account of the attack.
-“The little girl of our dreams was taken from us in such a horrible and unfair way that it completely broke us.”Alexandra and Sergio Aguiar, Alice’s parents, told the court.
This attack was “premeditated and planned”said prosecutor Deanna Heer.
In police custody, Axel Rudakubana declared that he was “very happy” that these children are dead, she added.
Videos from surveillance cameras showed the children fleeing the chaos of the dance hall, or a little girl, crying silently, being rescued in the toilet by a police officer.
“There is nothing that associates him with a political or religious ideology (…) His only objective was to kill,” said Deanna Heer, referring to the lack of qualification “terrorist” for these murders.
The police found in his home a machete, arrows, an Al-Qaeda manual in which he learned to make a poison, ricin, and numerous images of torture, decapitation or rape.
Fascination morbide
He was “fascinated by extreme violence”, and possessed, among other things, documents on the genocide in Rwanda.
Axel Rudakubana was born in 2006 in Wales, into a Christian family originally from Rwanda.
Diagnosed with autism, he was excluded from his college after bringing a knife there at the age of 13, but returned to attack his former classmates, whom he accused of racist harassment, with a hockey stick.
Many opportunities were missed to stop him: he had been reported three times to an extremism prevention program, notably for having learned about the killings in American schools during computer science class.
The attack sparked a wave of anti-immigration and Islamophobic riots in dozens of towns in England and Northern Ireland, after far-right accounts spread rumors online about the identity of the suspect.
