Having a life long love of performing, Herthum started acting professionally in the late 1970s. He appeared in commercials in and around his home state before moving to Los Angeles in 1982 to pursue his dream in earnest. The roles, however, did not come as easily. Herthum landed a mere three on-screen credits during the 1980s, before nabbing the part that would change his life forever. That role, of course, was as Deputy Andy Broom on the CBS's "Murder, She Wrote." The series starred Angela Lansbury as a mystery writer that moonlights as a detective, and racked up numerous Emmy nominations throughout its 12-season run. Herthum played Deputy Broom for five seasons, before starting his own feature-film production company in 1996. As the head of Ransack Films, Herthum earned acclaim for producing the award-winning films "Red Ridge" (2006) and "The Season Before Spring," the latter of which documented New Orleans' first post-Hurricane Katrina Mardi Gras celebration. In addition to producing, Herthum continued to act in movies and television shows throughout the '90s and 2000s, most notably "Treme" (HBO, 2010-13), "Breaking Bad" (AMC, 2008-13) and the 2010 horror hit "The Last Exorcism." Following a 2012 run as a power-hungry werewolf on "True Blood," he returned for the 2013 movie sequel "The Last Exorcism Part II." In 2012 Herthum was cast in a recurring role as a local gun expert named Omar on the A&E crime series, "Longmire." The show premiered its second season in May of 2013, with Herthum reprising his role.