The man, Moeketsi Tau, of Mabeskraal near Sun City, also hanged himself. He and his son, Kgotso, were buried yesterday in separate funerals at Selocha and Manamela sections in Mabeskraal.
Kgotso's heartbroken mother, Joyce Molefe, 40, relived the devastating day last week when her boyfriend vanished with the child after he had assaulted her and attacked neighbours who tried to intervene.
Molefe said she and Tau were separated and she was living with her daughter in Sunrise, not far from Paardekraal.
"We had been together for about nine years and initially everything was OK.
"I already had two daughters when we met and we had a son, Kgotso, who has now died," Molefe said, fighting back tears.
She said though Tau never physically attacked her, his words often cut deep.
"He would say some really hurtful things and also accuse me of taking my daughters' side whenever we had a disagreement.
"It got to a point where his constant abuse made me get sick physically," she said.
Molefe's daughters, who are from a previous relationship, are Botshelo, aged 23, and 19-year-old Lebogang.
Molefe described the day Tau disappeared with the child.
"He called out my name but I did not want to speak to him, so I kept quiet. I then heard Kgotso crying and I opened the door."
That gave an enraged Tau a chance to get his hands on her.
"He dragged me out of the house and on to the street. Kgotso was begging him not to hurt me but he would not listen."
And then, in a fit of rage, Tau allegedly slapped Molefe hard.
"I fell to the ground and the neighbour came running. They got into a fight and I managed to run," she said.
"But he outfought the neighbour and caught up with me. Another man from across the street also came but he was also defeated.
"He pushed me to the ground and picked up a rock and was going to crush me with it, but somebody hit him with a stone before he could," she said.
The two men then caught up with him and they once again fought.
"I managed to get Kgotso and run off to a nearby house. But when he [Kgotso] saw his father in a fight, he ran back to him.
"That is when he managed to grab the child and run away with him," she said.
Then under the cover of night, Tau disappeared with the boy.
"The two men tried to look for him, but were unable to find him. The police also tried without luck. I then went with them and slept over at the police station with the hope that he would come back.
"In the morning, his uncle told me what had happened," she said.
Molefe found out that three ropes were discovered in the house.
"It seems his intention was to hang me also. He had some serious issues. But I don't understand why he had to kill my son."