The family of a teenager who was murdered by two 12-year-old boys armed with a machete have said they are haunted by thoughts of how scared he must have been when he was killed.

In a victim impact statement read to the judge due to sentence the killers, both now aged 13, relatives of Shawn Seesahai described the Anguilla-born 19-year-old’s killing as tragic, unexpected and senseless, and having been committed “for no reason at all”.

The first day of a two-day sentencing hearing at Nottingham Crown Court was told both defendants – who blamed each other at their trial – still deny being responsible for the murder.

Mr Seesahai died after being stabbed in the heart and suffering a skull fracture on Wolverhampton’s Stowlawn playing fields.

A month-long trial was told that Mr Seesahai was shoulder-barged by the smaller of the two defendants, who “often” carried a machete with a 42.5cm-long blade, before being punched, kicked, stamped on and “chopped” at with the weapon.

The victim’s friend told the trial he was forced to run for his life but Mr Seesahai stumbled as he tried to flee from the boys.

His killers are believed to be the youngest defendants convicted of murder in Britain since Robert Thompson and Jon Venables, both then aged 11, were found guilty in 1993 of killing two-year-old James Bulger.

Mrs Justice Tipples, who is due to specify a minimum term and pass mandatory life sentences on Friday, was told there was “little precedent” for the case and the boys are thought to be the country’s youngest knife murderers.

The boys were allowed to leave the dock and sit beside relatives on the back row of the court as a family victim impact statement was read to the court by the Government of Anguilla’s international representative Dorothea Hodge.

Relatives of Mr Seesahai, who were forced to take out a loan to travel to the UK to view the 20-day trial, are watching the sentencing hearing via a videolink.

The family’s statement read: “We make this statement in relation to the tragic, unexpected and senseless murder of our beloved son and brother Shawn, who was tragically taken from us in November last year.

“As a family we are struggling in so many ways since Shawn was taken from us, especially in the horrific way in which he was taken.

“Losing a child is a parent’s worst nightmare. To put it all down in a statement on how it has impacted our lives would take more than a day to read.

“It has left a huge hole in the pit of our stomach which nothing can fill, we are devastated as a family, totally heartbroken and confused.”

The statement added that Shawn was incredibly close to his younger sister, who had always dreamed of being there for his wedding and him being there for hers.

The family members, including parents Suresh and Maneshwary and sister Shana, added: “Mentally it has been hard for any of us to function normally. None of us have had an unbroken night’s sleep since Shawn was taken from us.

“Every time I close my eyes all I can think about are what his last moments were and how scared he must have been. It continually breaks my heart.

“The impact on us as a family is devastating, its hard to believe that we will ever come to terms with what has happened.

“We will never get to see Shawn get married or have a family of his own. These things have been taken from us for what appears to be no reason at all.”

Mrs Justice Tipples ruled following the trial that the defendants cannot be identified by the media because of concerns surrounding their welfare.

During legal submissions on Thursday, the court heard the starting point for the minimum term to be imposed on both boys is set by sentencing guidelines at 13 years.

The court was told the minimum term’s starting point “is not a finishing point” and can be adjusted both upwards or downwards in accordance with aggravating or mitigating factors, which include the defendants’ ages.

Prosecutor Michelle Heeley KC submitted that the case was aggravated by the fact that one of the defendants had admitted he “regularly” carried the machete, and that fact that two offenders had jointly attacked one victim.

One of the boys admitted possession of the knife prior to the trial, while the other was found guilty of the same charge when they were both unanimously convicted of murder on June 10.

Both boys claimed the other had inflicted four wounds with the machete, after a dispute about sitting on a park bench.

Rachel Brand KC, defending the boy who admitted buying and owning the machete, told the court during mitigation: “He lacked, as a child, foresight of the consequences of his actions, and lacked, as a child, the ability to regulate his behaviour in the same way adults do.”

Urging the court to take into account the fact the boy had been “groomed” and exploited by older youths and young men in the wider community, Ms Brand added: “We say the evidence shows that his involvement was with his fists and feet and the co-defendant wielded the machete.

“He knows that he bears the responsibility for taking that machete to the scene.

“All he can do as a child struggling to express himself about what has happened is to say to the Youth Offending Team that he wishes he hadn’t taken the machete out with him.

“He wishes they hadn’t gone to the park. He wishes that this hadn’t happened.”

Paul Lewis KC, defending the other boy, said: “The prospects of rehabilitation in his case, we submit, are excellent.

“He had never been involved in any sort of criminality before. This was a one-off incident that was not premeditated – over in seconds – with admittedly tragic results.”

Sentencing in the case is expected to begin in the case at 11am on Friday.