Five security guards have been killed at the Pikitup Swartkoppie Depot in Devland, South of Johannesburg.
It is understood a group of gunmen stormed the facility on Tuesday and shot seven security guards.
Four of the workers died at the scene, while the fifth succumbed to gunshot wounds on Wednesday, two others are currently still in hospital.
The circumstances surrounding the shooting remains unclear.
The South African Municipal Workers’ Union (SAMWU) said none of the security guards personal belongings or any of the city’s property had been stolen.
“As Samwu, we are concerned that workers who are supposed to protect the city’s infrastructure are themselves left vulnerable to attacks. To make matters worse, these workers are not provided with weapons to defend themselves and the City’s property.”
Samwu has urged authorities to ensure the perpetrators are brought to book.