Defence experts speculated as to what may have caused the weapon to leave such a trail of bloodshed.

Jane's defence analyst Helmoed Romer Heitman said accounts indicated a sequence of events which would mean not any one element could be blamed. The gun reportedly jammed, there was an explosion and then a "runaway" gun fired wildly.

Heitman said the anti-aircraft gun was arguably the best of its kind in the world. It had been used widely and successfully for many years.

"Anything mechanical can malfunction; explosives are dangerous and computers go wrong," he said. "If the cause lay in computer error, the reason might never be found."

Arms industry boffin Richard Young said his company had been involved in two projects, called Dart and Catchy, which used the same anti-aircraft cannon.

On one occasion 10 years ago he witnessed problems with the cannons - including seeing one "seem out of control".

South Africa bought the guns during the apartheid era. "The Oerlikon anti-aircraft cannons acquired by the SADF from Switzerland were not fully automatic. Local developments provided them with automatic fire control.

"As an electronics engineer, I find it difficult to contemplate a control system failure mode that could lead to unintentional firing until the ammunition is spent. Such a system should fail to a safe mode. If this was caused by a faulty system design, or faulty electronic hard- or software then the engineers and the firm must be outed."

With acknowledgement to Sunday Tribune.