A judge has sentenced a Sydney taekwondo instructor to life in prison without parole for murdering a 7-year-old student and the boy’s parents. On Tuesday, Justice Ian Harrison said Kwang Kyung Yoo was motivated by jealousy over the family’s financial success. The 51-year-old had pleaded guilty to the murders, which took place in February last year. He strangled the boy and his mother at his martial arts academy and then stabbed the father to death at their home. Yoo had no prior criminal record and expressed remorse for his actions. The judge described the killings as horrific and senselessly cruel.