The scientists identified this snake-assassin as the brown button spider. It is widespread in various parts of the world, including North America and has neurotoxic venom that is as toxic as the black widow's. However, it is the first time when the fact of a spider eating a snake is documented.
The most likely candidate would be either l. cinctus (the east cape button spider) or l. indistinctus (the west cape button spider).
Here's a link the exact same pictures from 2008 that claims it took place in Australia: http://xo.typepad.com/blog/2008/09/spider-eats-snake.html
If that link is true, then the spider is most likely a redback spider (l. hasseltii).
Either way... KILL IT WITH FIRE!!!!
http://www.hoax-slayer.com/spider-catches-snake.shtml