The 13-year-old boy who was arrested in connection with the murder of a Mondeor High School pupil, appeared in the juvenile section of the Johannesburg Magistrate's Court's on Thursday. 

The case was postponed to Friday to give him an opportunity to be assessed by a probation officer. 

"The probation officer will then compile a report that will be presented to the court so that a process of conducting a preliminary inquiry can be kickstarted," said National Prosecuting Authority spokesperson Phindi Mjonondwane.

He was in a place of safety, Mjonondwane added.

The boy was arrested on Wednesday evening.

Gauteng police made a breakthrough on Thursday morning when two more teens, believed to be from a nearby school, were nabbed.

Earlier on Thursday morning, Gauteng police spokesperson Captain Kay Makhubele said the arrests had taken place in Soweto and Naturena respectively and that the suspects were both aged 15.

Nineteen-year-old Kulani Mathebula was on his way to school on Wednesday morning when he was stabbed to death - just 10 minutes away from his school's premises.  

The Grade 11 pupil died on the scene.

Mondeor High School principal Vangelia Nicolaou was among the first at the scene.

She said that when she arrived, Mathebula was still breathing and his eyes were open. Next to him, lay his blazer, bags and shoes.

ER24 spokesperson Russel Meiring said Mathebula had a stab wound to his chest and there were no signs of life when paramedics found him.

He said CPR was immediately initiated to try to revive him.