I just downloaded their page (not via browser) and saw that they've just taken this code: http://pastebin.com/grNdf3Mj (safe to visit, plaintext) and wrapped the js in a self invoking function. At the end of the function they included a call to another function which starts firing.

The original script required users to click the fire button but this does it by itself on load.

Strangely the current 'attack' page also features the google ad script, a twitter widget, kontextua ad script and whos.amung.us visitor tracking.