Officer Kilroy was critically injured when he and his horse was struck by an oncoming automobile while on mounted patrol. Officer Kilroy and Officers John Riley and Frank Lockman were crossing the Kingshighway viaduct over the Mill Creek Valley and were checking on a disabled car when another car entered the area at a high rate of speed. The vehicle struck Officer Kilroy's horse, throwing Officer Kilroy approximately thirty feet, knocking him to ground and fractured his skull. Officer Kilroy was taken to City Hospital by private vehicle but died a short time later. The driver of the vehicle was brought to trial for criminal negligence but acquitted by a jury.

Officer Kilroy, born in Ireland, was survived by his wife, Marie, and four children. Interred: Calvary Cemetery.