(written from a Production point of view)
He began his career as a grip on the 1981 film Wolfen and moved on to become a production assistant on the films Sophie's Choice and Trading Places.
Gerrity was a second assistant director on the television series Twin Peaks and films like Predator 2 and Dutch. He later worked as first assistant director for the second unit of the films Patriot Games, Tommy Boy, Eraser, Jerry Maguire, The Replacement Killers, Blue Streak, and Supernova. He was also first assistant director for the first unit of the 1994 film Blown Away and for the creature unit on The X-Files: Fight the Future.