|This article is about the former Showrunner. You may be looking for the other Glenn in the Comic Series, TV Series, Video Game, Road to Survival, No Man's Land, Social Game, Assault, The Escapists or Atlanta Run, or the Novel Series character.|
Mazzara was born in Manhattan and grew up in Queens, New York. He attended NYU, and earned a masters in English. He worked as a hospital administrator in New York before moving to Los Angeles to pursue a career as a writer in 1998.
He was a story editor and writer for the fourth and fifth seasons of Nash Bridges. He joined the drama series, The Shield as an executive story editor and writer for its first season in 2002, was promoted to producer for the second season while continuing to write, to supervising producer for the third season, to co-executive producer for the fourth season, to executive producer for the fifth season, and left midway through the sixth season in 2006.
- "18 Miles Out" (with Scott Gimple)
- "Better Angels" (with Evan T. Reilly)
- "Beside the Dying Fire" (with Robert Kirkman)