We're not used to thinking of them this way. But many advanced military weapons are essentially robotic -- picking targets out automatically, slewing into position, and waiting only for a human to pull the trigger. Most of the time. Once in a while, though, these machines start firing mysteriously on their own. The South African National Defence Force "is probing whether a software glitch led to an antiaircraft cannon malfunction that killed nine soldiers and seriously injured 14 others during a shooting exercise on Friday."
Essentially, they were using live ammo for a training exercise, and the cannon didn't fire when it should have. Shortly thereafter, it began firing uncontrollably.
I really wonder how far mankind will go before deciding there should be limits to everything?
Update: Here's a video of a similar incident a few years back:
Warning: Turn your sound down, the first second or so is obnoxiously loud
Noah Shachtman has some interesting commentary about the video over at Wired.