A six-year-old boy was shot and wounded on Tuesday in a robbery at the Mayflower Post Office pension point near Ermelo, Mpumalanga police said.
Two other people were wounded when an armed gang struck.
"About eight heavily armed men held the tellers at gunpoint and forced them to open a safe," said Colonel Leonard Hlathi.
"They took an undisclosed amount of cash. As they fled the scene, the robbers fired shots randomly, hitting three bystanders."
They sped away in a white Toyota Hilux and a green Toyota Avanza.
Police are investigating a case of business robbery and attempted murder.
No arrests have been made.