Two 12-year-old boys are thought to have become the youngest knife murderers in the UK after being found guilty of killing a 19-year-old in a machete attack.

Warning: This story contains details readers may find distressing

On Monday, jurors unanimously convicted the pair, who are believed to be youngest defendants convicted of murder in Britain since Robert Thompson and Jon Venables, both aged 11, were found guilty in 1993 of killing two-year-old James Bulger.

Shawn Seesahai, 19, died after the attack on 13 November last year.

He was struck on his back, legs and skull. The fatal wound to his back was more than 20cm deep and “almost came out” of his chest after going “through his heart”.

Two 12-year-old boys denied murdering Mr Seesahai but prosecutors said they were jointly responsible for the savage attack.

Following the verdict, the detective who led the hunt said his experienced team were left in shock at the age of the killers.

“I have been a police officer for 20 years and this isn’t the first time I’ve been out to a young man who has lost his life in a really violent way,” said Detective Inspector Damian Forrest, of West Midlands Police.

“But to then find out that two 12-year-olds were responsible was shocking and made us all on the investigation team stop and pause and think about things.

“But I have got a really professional team with lots of experience and we gathered our thoughts, adapted our policies and our processes appropriately, and carried on with the investigation from there.”

Mr Seesahai, originally from Anguilla in the Caribbean, had been staying in Birmingham while recovering from cataract surgery.

He and a friend had walked to a park in Wolverhampton where they encountered a group of children.

Prosecutors said despite the fact Mr Seesahai had “offered no violence, nor done anything to offend”, he became the victim of a brutal attack.

Neither boy can be named because of their age.

Unprovoked savagery

Prosecutors said one of the boys deliberately “shoulder brushed” Mr Seesahai that evening and then pulled a machete from his trousers.

Mr Seesahai’s friend managed to escape but Mr Seesahai ended up on the floor where prosecutors say he was punched, kicked and knifed by the two boys.

He was hit so hard to the skull with the machete that a “piece of bone had come away”.

He also sustained slash wounds to his leg and, most significantly, an injury from the machete that entered his body from his back, went through his ribs and into his heart.

“These two boys engaged in a joint attack upon a man who had done nothing wrong, a man with no weapon, who was utterly defenceless on the ground,” said Michelle Heeley KC.

Mr Seesahai’s mother Manashwary described her son as “very loving”.

“He’s always there for us, a very protected child. He helped his father [at work] with all the tools, he helped me [at] home with the chores, he loved to do that.”

Shawn’s father Suresh says his son used to help him with his work in construction.

“He was always with me, from the time he was born and growing up. When he’d have been around 16 he started to work with me. Whatsoever he knew that I’d need help [with] he’d always be there for me.”

‘This world is a different world’

Mr Seesahai’s parents said Shawn had wanted to build a life in the UK and pursue a career in engineering. They said he was recovering well from his operation and the family had planned to join him in the UK so they could all be together.

Mrs Seesahai says her son was ambitious.

“He didn’t finish school, so after he came here and finished the eye surgery, he said when he felt better he’d finish off school and have his dream.”

“He’d always say ‘Mom, I want to work, I want my own house, I want my own car.’ He’d always say ‘Mom, I will be shining’.”

Mr Seesahai’s father spoke of the need for parents to be more aware of what their children might be up to.

“You don’t know what these kids have. This world is a different world. Kids are dangerous now and if we don’t pay attention to our kids it will happen every day.”

Defendants blamed each other

Both boys blamed each other for the attack. One of them admitted to possessing the weapon that was used.

He was the first to give evidence in court and said that he and his co-accused had been sitting on a bench in the park with a female friend when they were approached by Mr Seesahai and another man.

He said Mr Seesahai towered over them and told them to “move from here”.

He said he told Mr Seesahai’s companion to “get your friend out of my face”.

The boy said Mr Seesahai grabbed him in a headlock and that his co-defendant ended up holding the machete and “side-stepped” towards them.

“Shawn let me out of the headlock and started running and then his shoe came off, and then he tripped,” he said.

The boy said both defendants ran after Mr Seesahai and the other 12-year-old then began striking his legs with the knife.

The first defendant said he told his friend to stop and didn’t realise that Mr Seesahai had been stabbed in the back.

He said that after the attack he had retrieved the knife.

Machete discovery

Police later found the machete under his bed. He said he had purchased the weapon for £40 a couple of months before the killing.

He used bleach to clean the blood-stained knife, saying he got the idea from a music video, before hiding it under his bed.

The second 12-year-old gave a very different account, claiming his friend had stabbed Mr Seesahai and that he had been “nowhere near” him during the attack. He also denied having the machete in his own hands as the attack unfolded.

He told the court he had pushed Mr Seesahai off his friend, at which point the 19-year-old “grabbed on” to him, forcing them both to the floor.

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Bloody attack

“I fell on the concrete,” he said. “Shawn fell on the grass.”

He said his co-defendant then ran after Mr Seesahai, who tripped when his shoe came off, and stabbed him more than once.

He said his friend had blood “all over his hands” and on the cuff of his fleece.

When police seized the boys’ phones they found photos of knives.

The 12-year-old who had purchased the machete said he had sent photos showing himself holding the weapon because he “thought it was cool”.

The boys have been held in secure accommodation since the attack.

Jonathan Roe, Senior Crown Prosecutor for CPS West Midlands, said: “This was a horrifying and random act of brutality, perpetrated by two 12-year-olds who should not have been spending their time arming themselves with a machete and preparing to take a life.

“Today’s conviction should send a clear message to those who feel it appropriate to arm themselves with knives or blades – no matter how you may try to justify it, you will face the consequences of your actions.”