Williams was first hired to work as a writer on the TV series 24, writing one of its first-season episodes. He was then promoted to its story editor in the fall of 2002. After writing two second-season episodes and one third-season episode, he then left to work on ER. There, Williams was a co-producer and writer for the show's twelfth season, writing two of its episodes before being promoted to producer for its thirteenth season. He also worked on Criminal Minds as a producer and writer. In 2016, Williams was assaulted by Thomas Gibson during a heated argument over creative differences. This resulted in Gibson's dismissal from the show.