Johannesburg - The man accused of killing two 8-year-old cousins told the Germiston Magistrate's Court on Thursday that the investigating officer had threatened that he would be given rat poison in prison. “The investigating officer trapped me in the cells and said he will make sure I get rat poison in jail,” Bongani Mavimbela told a packed courtroom.The balding man was dressed in a green overall top and grey pants. His face was swollen and his eyes were bloodshot. He showed no emotion as he stood in the dock. Germiston locals caught and beat him up on Monday. He then allegedly revealed where the children's bodies were.The 40-year-old initially said he did not want a lawyer, but later agreed to engaging one when the magistrate pointed out the seriousness of the case. He faces two charges of murder. The case was postponed to August 19 for a bail application. Mavimbela would remain in custody.Used to call him 'uncle'He was arrested after he was seen on CCTV footage leaving a shop, next to the block of flats in Railway Street where Kefilwe and Thato Motaung lived, with them.The CCTV footage shows Kefilwe, wearing a pink top, holding the hand of the alleged killer. She glances over her shoulder at her cousin Thato. Shortly afterwards, Thato runs after her. The boy and girl had been bludgeoned to death. Their bodies were hidden under plastic covers in an abandoned building near the Germiston mortuary, about 2km from their home. Local residents sang and chanted outside the court on Thursday morning. Some held posters reading, “Stop child rape” and “Germiston Monster”. The children’s grandfather, Lelala Motaung, told News24 on Wednesday that the children used to call the man uncle. "He was like their own. They used to call him uncle whenever he came to visit us," Motaung said. He used to visit the Motaungs often and was served meals.