Two boys in Britain who were 12 when they stabbed a stranger to death with a machete were sentenced on Friday to at least eight and a half years in prison. They are the youngest people convicted of murder in the U.K. for more than 20 years.

The now 13-year-old defendants, who can’t be named because of their age, were convicted in June of murdering 19-year-old Shawn Seesahai. The victim, who had moved to England from the Caribbean island of Anguilla, was stabbed in the heart after encountering the boys on playing fields in the city of Wolverhampton in November 2023.

Judge Amanda Tipples sentenced the two boys to life with a minimum term of eight and a half years.

Each of the accused blamed the other for attacking Seesahai with a machete after a dispute with the victim about sitting on a park bench. The judge said that she couldn't be sure which defendant had inflicted the fatal wound.

“What you did is horrific and shocking,” the judge said at Nottingham Crown Court. “You did not know Shawn, he was a stranger to you. You both killed Shawn in an attack that lasted less than a minute when he asked you to move.”

Chief Superintendent Kim Madill of West Midlands Police said the “shocking and saddening” case revealed the human cost of knife crime.

“The impact of knife crime is devastating no matter where you live in the country,” she said. “This is an issue that affects us all. Much work has been done and we have had successes in some areas. However, this is clearly not enough.”

The pair are believed to be the youngest defendants convicted of murder in the U.K. since Robert Thompson and Jon Venables, both 11, were found guilty in 1993 of killing 2-year-old James Bulger. They had abducted the toddler from a shopping center and beat him to death by an isolated railway line in northern England.