A 15-year-old boy has been detained at His Majesty’s pleasure for murdering a shopper after a row in an Asda supermarket toilet.
The teenager travelled to the Worcestershire town planning to rob and deal drugs.
All youths, who cannot be named due to their age, denied murder, manslaughter and violent disorder in the trial hearing in November.
The killer, from Birmingham, who cannot be named for legal reasons, travelled with other boys by train to the town on March 8 last year, where Mr Kirwan was subjected to a minute-long attack near the entrance of an Asda store.\
Jurors cleared the three other youths – now aged 14, 15 and 16 – of murder and manslaughter but found them guilty of violent disorder. The older boy had also previously admitted having the 12-inch kitchen knife used for the fatal attack.
They were each handed youth rehabilitation orders.
Sentencing the killer at Birmingham Crown Court on Wednesday, Mr Justice Fraser, told him: “Mr Kirwan’s murder is a tragedy and so utterly senseless it defies description.
“It is also a stark reminder if society were to need one of the danger of young people carrying knives with them as a matter of routine.”
The court heard that Mr Kirwan was knifed in the chest after 'challenging a group of youths for messing about in the toilets' at the store in Jinnah Road on March 8 last year.
Jurors convicted the boy - then aged 14 - of murder after hearing how Mr Kirwan was knifed in the heart by youths acting as a part of a masked gang which "terrorised" members of the public in the town.
The killer, from Birmingham, travelled by train to the Worcestershire town as part of a group before launching the minute-long attack near the entrance of the store.
Jurors, after the 10-week trial, cleared three youths - two aged 14 and one aged 16 – of murder and manslaughter but found them guilty of violent disorder.
The boy, aged 16, was acquitted of murder, manslaughter and violent disorder, having claimed he was not involved in the fatal confrontation and could not have predicted it.
Mr Kirwan's wife paid tribute to him after the conviction, calling him "the better half" of their relationship,
Ian’s wife said: “Ian was a big kid; a wonderful person who was full of love, kindness, and generosity. I really miss him in my life.
"I miss his ways that would drive me crazy but he always made me and our family and friends happy and there was never a day that we wouldn’t laugh when he was with us.
"Ian would always make us feel protected, secure, and safe."
The youth was detained for a minimum of 14 years.