Justin Bieber got more than a car for his 16th birthday. He won four awards at the American Music Awards Sunday! Bieber won trophies for pop/rock male, breakthrough artist, album of the year, and artist of the year. "I can't stop smiling," he said of his clean sweep. When Bieber won artist of the year — the top AMA honor — he invited the man who discovered him up the the stage to share in the glory. He described Usher as "not only my mentor but my best friend and my big brother."