Robert Knox. Photo: The Rob Knox Foundation

Robert Knox never got the chance to see himself in what could have been his breakout role. Days after he finished filming Harry Potter and the Half-Blood Prince — in which he played Marcus Belby — the 18-year-old actor was stabbed to death.

The incident occurred on May 24, 2008 outside a pub in London. PEOPLE reported at the time that Knox had been trying to shield his younger brother Jamie from a man with a knife.

Karl Bishop, 21, was charged with the murder.

During Bishop’s trial, prosecutors said he had acted out of revenge, claiming that he had lost a fight with Knox and his friends the week before, the BBC reported.

“I’m going to come back next week and someone’s going to die,” Bishop reportedly said, according to the BBC.

Robert Knox. The Rob Knox Foundation

Bishop and Knox had another encounter earlier on the night of the murder as well, after which, the BBC reported, Bishop went home and armed himself with two knives.

Eventually, Bishop confronted Jamie, at which point Knox rushed out of the bar. The actor was stabbed five times, including once in a major artery.

Four of Knox’s friends were also injured in the attack, with one suffering permanent spinal damage, The Times reported.

Colin and Sally Knox. UPPA/Zuma

The BBC reported that when Bishop was told he was being charged with murder, he said “yeah sweet,” according to police.

“There was no real reaction to being told that he was being arrested for murder,” police officer Craig Reid said, according to the BBC, which also reported the officer told the court Bishop showed “no remorse.”

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The officer further alleged that Bishop was more upset about missing a Ricky Hatton fight than being arrested for murder.

Bishop was ultimately convicted of murdering Knox and sentenced to life in prison, The Guardian reported.

Despite his conviction, The Times reported that Bishop refused to hear victim impact statements, smiled at friends in the courtroom and even giggled at one point.

During his sentencing, a judge told Bishop, “I do not think it is proved that you intended to kill Robert Knox.”

Karl Bishop. Handout

But the judge added that, “The truth is that you simply could not care less whether you killed him or not,” ITV reported.

Knox was already signed up to reprise his role as Marcus Belby in Harry Potter and the Deathly Hallows Part I, but was robbed of the opportunity. The Half-Blood Prince premiered in July 2009, months after Bishop was sentenced to life in prison.

Before Harry Potter, ITV reported that Knox had appeared in different television shows, including episodes of comedy series After You’ve Gone. 

“Rob was happy, outgoing and a fun person to be with,” Knox’s father, Colin, previously said in a statement. “Rob always put everyone before himself, was always the first person to stand up against wrong. He achieved so much in his short life.”