Soga and his colleague, Constable Siyabonga Nani, 41, had reportedly been responding to a complaint when several men in a double-cab bakkie, who were ostensibly in need of police assistance, approached him, News24 previously reported.
One of the men on the passenger's side drew his firearm and shot Soga. He died on the scene.
The men then ordered Nani, who was not armed, to move his colleague's body from the driver's seat to the back of the state vehicle.
Nani was then allegedly forced into the back of the patrol vehicle.
Police spokesperson Lieutenant Colonel Philani Nkwalase said: "Several shots were fired at the police vehicle, killing [Soga] instantly, police were disarmed and their vehicle hijacked to commit [an] armed robbery at a local store where they got away with R6 000 cash, a firearm and a bakkie belonging to the store owner, which was found abandoned near Mqanduli."
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On 6 December, the first four accused were arrested. Six firearms, including Soga's service pistol, were found and seized.
Four more accused were arrested from December to March.
Two of the nine accused were released on R3 000 bail and the case against the remaining accused was postponed to the 27 August for a bail application.