Convicted murderer Sandile Mantsoe has been sentenced to a cumulative 32 years in prison after murdering his ex-girlfriend Karabo Mokoena.There were audible gasps in South Gauteng High Court on Thursday as acting judge Peet Johnson described Mantsoe as the devil in disguise.Mantsoe was sentenced to 30 years for the murder, five years for assault and four years for the attempt to defeat or obstruct the course of justice. Part of the sentences for the assault and attempt to defeat the course of justice, will run concurrently with the murder sentence.His effective sentence amounts to 32 years, the court said.He said the sentence should serve as a warning to others that abuse against women will not be tolerated. During sentencing proceedings earlier in the morning, Mantsoe said: "I am very remorseful. I knew a lot of things about her that she was trying to escape from. Both me and her were very secretive. I feel like I had failed her. I felt like the good that we have worked on... I disappointed her. It hurt me because I inspired her a lot."On Wednesday, the South Gauteng High Court in Johannesburg also found Mantsoe guilty of defeating the ends of justice and of assault with intent to do grievous bodily harm.Mokoena's charred remains were found by a passer-by in Lyndhurst, Johannesburg in April 2017.