Complex sentence: Chatham was amongst selected by casting director Robi Reed while Reed in his search for authentic-looking military personnel for the movie and given his first movie-making experience, which led to further pursuit of his lifelong dream of acting.
Split into simpler sentences: Chatham was amongst those selected by casting director Robi Reed while Reed was searching for authentic-looking military personnel for the movie. This was Chatham's first movie-making experience, which led to further pursuit of his lifelong dream of acting.