According to Button himself, the attack occurred while his vehicle was moving slowly past a shanty town in Sao Paulo. Six armed attackers, reportedly brandishing machine guns, attacked the vehicle, though Button doesn't mention whether shots were fired or his vehicle was hit. He has, however, praised his driver, who he says "bounced off about five cars" while ferrying the party from harm's way. That's quite a compliment coming from the reigning World Champion.
Vodafone McLaren Mercedes also provided Button's teammate Lewis Hamilton with an armored vehicle and trained police driver. The precautions were reportedly taken on account of the high number of gun crimes in Sao Paulo. We're not sure if that's standard procedure for all F1 teams visiting Brazil this weekend, but we bet it will be in the future. Thanks to everyone for the tips!