Netcare 911 spokesperson Chris Botha said paramedics declared the guard dead at the scene at the Phoenix Plaza.
Sources told News24 that the guard was walking down a passageway of the mall when he was shot and sustained a number of gunshot wounds.
It is unclear how many attackers there were, but the robbers seized the cash box that the guard was carrying. It is not known how much cash was in the box.
It is understood that the man from Fidelity Guards had left a DStv outlet when he was attacked.
Police spokesperson Thulani Zwane confirmed the shooting, but could not provide further details.
Comment could not immediately obtained from Fidelity Security.