|This article is about the crew member. You may be looking for the other crew member, the actor, the voice actor, the Social Game character, or the Video Game character.|
Fierro began his television career as a freelance writer. He wrote two scripts for the first season of Resurrection Blvd. in 2000. In 2002, he returned as a co-producer and writer for the third season and contributed a further three episodes.
In 2004, Fierro joined the crew of The Shield as a writer and co-producer. He wrote three episodes for the third season. He was promoted to producer in 2005 and contributed a further two episodes to the fourth season. He continued to receive more responsibility and became a supervising producer for the fifth season writing two more episodes. He was made co-executive producer for the sixth season and wrote two more episodes. After filming completed on the sixth season of The Shield, Fierro became a co-executive producer for the sixth season of 24 and wrote an episode. Fierro returned to The Shield for the seventh and final season and served as an executive producer and wrote three episodes.
After completing work on The Shield, Fierro became a consulting producer and writer for the third season of Dexter. He was nominated for a Writers Guild of America Award at the February 2009 ceremony for Best Dramatic Series for his work on the third season of Dexter. Fierro was reunited with The Shield producer Charles H. Eglee on Dexter.