Current rumors suggest that this was a GoonSwarm infiltration, but as of this posting this is unconfirmed. Multiple sources suggest that a director of the alliance has defected to GoonSwarm, stealing billions worth of assets, and compromising the sovereignty that Band of Brothers had previously established.
Massively.com will keep you up to date as more information is known about this major EVE event.
Update: GoonSwarm has released a audio file (NSFW), allegedly explaining what happened. This account is still, however, unconfirmed.
(Thanks, Six Strangelove!)