Putin has long been using that trick in Russia - the last 7 opposition party leaders have all been assassinated. Showing how seriously he takes such political violence, Putin has taken personal charge of all the investigations. Sadly nobody has yet been charged in any of them. Obviously this is through no fault of Putin who is sincerely putting his KGB training to good use trying to find the assassins.

But the ANC has a problem neither the Nats nor Putin had - an abundance of free press and a highly independent judiciary. This makes high-level assassinations fairly rare, and when they do happen they are more often to eliminate internal competition within the party or among it's corrupt friends (KZN gets lots of that on the lower rungs) but also consider Lolly Jackson, Bret Kebble etc. - situations where the state doesn't really have to risk getting it's own hands very dirty.

Unlike Russia, the odds of being able to sweep that away without repercussions are much lower now.