A schoolboy has described screaming at a 16-year-old boy to “stop”  after seeing him stab another boy in a Suffolk town.

Giving evidence in a pre-recorded video, the witness said he had been walking to a shop in Haverhill with Harley Barfield when they saw a 16-year-old boy who had previously gone out with Harley’s girlfriend.

The witness said he was aware of tension between the two boys because of Harley’s relationship with the girl and was aware they didn’t like each other.

He said the 16-year-old had confronted Harley saying: “If you want to bang me out then do it” to which Harley had replied: “I might have to if you carry on like this.”

He said the 16-year-old had swung a punch at Harley which missed, and Harley had punched him back and made contact with him.

The witness had called Harley’s girlfriend to tell her about the confrontation and then saw the 16-year-old boy slash Harley with something.

He said Harley had looked down and started running and he heard him say: “I’ve just been stabbed. Help.”

As he ran away, Harley had tripped over and the witness said he saw the 16-year-old stab Harley twice while he was on the ground.

The witness said he heard Harley screaming “stop” at his attacker and he had also screamed at the boy to stop.

The 16-year-old boy, who can’t be named because of his age, has denied murdering Harley in January this year but has admitted manslaughter and possessing the knife used to kill Harley.

It has been alleged that the defendant armed himself with a kitchen knife and lay in wait for Harley before confronting him in a “jealous rage” and trying to goad him into a fight.

Riel Karmy-Jones KC, prosecuting at Ipswich Crown Court, said the defendant and Harley, who she described as being in a “love triangle” had thrown punches at each other before the 16-year-old took a knife out of his pocket and stabbed Harley several times.

She described the attack as “frenzied” and said that Harley received cuts to his neck, head, cheek and lip as well as three stab wounds to the left side of his chest, one of which penetrated his heart.

A member of the public had performed CPR on Harley who appeared to have stopped breathing, said Miss Karmy-Jones.

After the incident the 16-year-old had run from the scene and had disposed of the knife.

He went to his grandparents and allegedly told them to call the police as he had stabbed someone.

An air ambulance was called to the scene of the stabbing and Harley was airlifted to hospital where despite the efforts of doctors, he died two days after the stabbing on January 11.

A post-mortem examination showed he had died from multi-organ shock caused by a lack of blood circulation.

Miss Karmy-Jones said that following the stabbing it was discovered that the 16-year-old had carried out Google searches on “how to stab someone without getting stabbed back” and “how long do you get for murder?”

“His phone shows he’d been thinking about murder for some time,” said Miss Karmy-Jones.

“The prosecution case is that he was so obsessed with his ex-girlfriend and jealous of her relationship with Harley that he murdered for her.”

Miss Karmy-Jones said the defendant had been diagnosed with autism spectrum disorder ( ASD) and his defence was that his ASD diminished his responsibility for killing Harley.

The trial continues.