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 served as a consulting producer and writer for the second season of medical drama series Hawthorne in 2010.
Fierro again worked with Eglee on the first season of AMC drama series The Walking Dead.