Horstmann began his film career in Atlanta, Georgia in the early 1990s, first as an editor and then a director at Turner Broadcasting[4] - working on the team that launched TNT, TCM and the Cartoon Network.

[4] After completion of the film, Horstmann founded Triple Horse Productions,[4] where he directed and produced hundreds of television commercials and title sequences for Coca-Cola, Under Armour, Home Depot, the NFL, NBA and Major League Baseball.

Horstmann's first television outing was a highly rated pair of History Channel prime-time specials exploring the mystery of the lost colony of Roanoke.

Notable film credits include The Case for Christ, starring Mike Vogel, Erika Christensen and Faye Dunaway, and the feature documentary, that Horstmann also directed, entitled Fallen Angel: Call Sign Extortion 17 investigating the contradictions surrounding an Army helicopter in Afghanistan that was shot down carrying 17 members of the elite Navy SEAL Team 6, the unit that killed Osama Bin Laden.

Horstmann's 2023 scheduled film releases as Producer include Southern GospeI - a 60's era faith drama, Love, Courage and the Battle of Bushy Run - an action packed story of the decisive battle that ended the Seven Years War in 1763, the southern gothic action picture, The Daylong Brothers starring Keith Carradine, the faith drama On A Wing And A Prayer with Dennis Quaid directed by Sean McNamara, and a family friendly limited series for Sony/Affirm entitled Shadrach - the six episode, coming of age tale of a little girl and her horse also directed by McNamara.