Just a few hours ago, EVE Online alliance GoonSwarm released a statement that the US official killed was apparently GoonSwarm director and former Council of Stellar Management member Sean "Vile Rat" Smith. Players, CCP developers, and GMs have begun leaving their condolences on the official EVE forums. According to those who knew him, Vile Rat was a well-loved player and a respected leader whose actions indirectly touched the lives of every EVE player. Massively extends its own condolences to his family and friends.
[Update: In the time since this story was published overnight, the BBC has updated its coverage, noting that a total of four Americans were killed in the attack, the US Ambassador to Libya and Sean Smith among them.]