Robert Knox played Marcus Belby in Harry Potter And The Half-Blood Prince, and was set to reprise the role in Deathly Hallows. The Harry Potter series was meant to be his big break. However, just a few days after filming his role, on May 24th 2008 the 18 year old actor was stabbed to death outside a bar while defending his younger brother during an altercation. His killer, Karl Bishop, went into a rage after losing a fight earlier in the night. He was found guilty of Knox's murder in 2009 and given a life sentence.