LONDON >> A teenager who stabbed three young girls to death at a Taylor Swift-themed dance class in England was sentenced Thursday to more than 50 years in prison for what a judge called “the most extreme, shocking and exceptionally serious crime.”

Judge Julian Goose said Axel Rudakubana , 18, “wanted to try and carry out mass murder of innocent, happy young girls.”

Goose said that he couldn’t impose a sentence of life without parole, because Rudakubana was under 18 when he committed the crime.

But the judge said he must serve 52 years, minus the six months he’s been in custody, before being considered for parole, and “it is likely he will never be released.”

Rudakubana was 17 when he attacked the children in the seaside town of Southport in July, killing Alice Da Silva Aguiar, 9, Elsie Dot Stancombe, 7, and Bebe King, 6. He wounded eight other girls, ages 7 to 13, along with teacher Leanne Lucas and John Hayes, a local businessman who intervened.

The attack shocked the country and set off both street violence and soul-searching. The government has announced a public inquiry into how the system failed to stop the killer, who had been referred to the authorities multiple times over his obsession with violence.

Rudakubana faced three counts of murder, 10 of attempted murder and additional charges of possessing a knife, the poison ricin and an al-Qaida manual. He unexpectedly changed his plea to guilty on all charges Monday.

But he wasn’t in court to hear sentence passed Thursday.

Hours earlier he had been led into the dock at Liverpool Crown Court in northwest England, dressed in a gray prison tracksuit. As prosecutors began outlining the evidence, Rudakubana interrupted by shouting that he felt ill and wanted to see a paramedic.

Goose ordered the accused to be removed when he continued shouting. A person in the courtroom shouted “Coward!” as Rudakubana was taken out.

The hearing continued without him.

Prosecutor Deanna Heer described how the attack occurred on the first day of summer vacation when 26 girls were “gathered around the tables making bracelets and singing along to Taylor Swift songs.”

Rudakubana, armed with a large knife, intruded and began stabbing the girls and their teacher.

The court was shown video of the suspect arriving at the Hart Space venue in a taxi and entering the building. Within seconds, screams erupted and children ran outside in panic, some wounded. One girl made it to the doorway, but was pulled back inside by the attacker. She was stabbed 32 times but survived.

Gasps and sobs could be heard in court as the videos played.

Heer said two dead children “suffered particularly horrific injuries which are difficult to explain as anything other than sadistic in nature.”

One dead girl had 122 injuries, while another suffered 85 wounds.