This sounds a bit like the bad old days. Excerpts from this article on News24.
Mathe was released on warning in June because the State did not have enough evidence against him.

The State's case against him apparently had been based on "testimony" of Solly Hangwane, 45, one of two State witnesses who died in police detention.


Hangwane and another State witness, Frans Mampane, 36, died in police custody.

Another State witness apparently escaped from a house where he had been under police guard.
Not much to indicate the deaths are going to be scrutinised much. And probably nothing to do with the fact that members of the police are implicated in the robbery.