As you can hear from the clip below the crowd went wild when he appeared on the screen.
Pattinson filmed the short thank you speech while filming in Baton Rouge, Louisiana, where most of "The Twilight Saga: Breaking Dawn" Parts one and two will be filmed. The footage was presumably recorded before Robert Pattinson, Kristen Stewart and other members of the cast traveled to Brazil to film Bella Swan and Edward Cullen's honeymoon scenes.
In the message he tells the crowds that he's currently acting and on the set of "Twilight Saga: Breaking Dawn". The finished off the clip be apologizing for not being there and thanked his fans for the award again.