From Halopedia, the Halo wiki
This article is about the Bungie animator. For other people with this name, see William.
William O'Brien, also known as Bill O'Brien, is an American animator, artist and video game producer. He is also a current employee of Bungie. Born and raised in Boston, Massachusetts, USA, he attended art school and majored in animation. He specializes in both 2D and 3D animation.
O'Brien joined Bungie in 2002. He was credited as one of the animators for Halo 2, Halo 3, and Halo 3: ODST. In Halo Reach, the game he claimed to be proudest of any game he has ever worked on, he worked as the animation lead.