Deputy O'Leary died as a result of rheumatism of the heart after becoming ill during the search for the murderer of Detective Frank Campbell and Sergeant John Brame, of the Fresno Police Department. At the time of the murders Deputy O'Leary was on sick leave with a case of the flu but refused to stay home and helped officers with the search for the killer. As a result he became even more ill which led to his death two months later.
Deputy O'Leary had been in law enforcement on and off for almost 20 years. He was survived by his wife, daughter, and two sons.