A 41-year-old man, who was supposed to go on trial for a double murder in November, shot and killed his mother before turning the gun on himself on Tonetti Farm near Low's Creek in Mpumalanga on Wednesday afternoon.
According to the police, the man had attacked his mother during an argument.
"Both stayed on the same premises but in different houses," provincial police spokesperson Brigadier Leonard Hlathi said in a statement.
"It is suspected that they had a dispute and the man went to his mother's house, where she was attacked. They were both certified dead on the scene by medical practitioners."
Hlathi said the man was due to appear in the Gauteng High Court in Pretoria, sitting in Barberton, on November 5 to answer to two murder charges.
He was accused of murdering a 72-year-old farmer and his 66-year-old employee in 2017. Both men were killed after they accused him of stealing the farmer's giraffes.
"One of the employees narrowly escaped [the attack] by hiding in one of the rooms," Hlathi said.
The police believe the firearm that was used in the murder/suicide belonged to the man's wife.
Hlathi said an inquest was opened and the investigation into the murder and unlawful possession of a firearm would continue.