NORMAN, Okla. (KFOR) — A K-9 deputy has suddenly passed away and an investigation is now underway. The Cleveland County Sheriff's Office says K-9 Dolar died unexpectedly Thursday while at a training session. LOCAL NEWS: Cleveland Co. Commissioners seek answers after recent jail deaths ignite concerns Video of K-9 Dolar that was taken when he first arrived on duty four years ago. Deputies say he was a great canine and a better friend. "When it's time to work he's always ready to work," a deputy said. "Me and him got real close." Dolar was assigned to the county's detention center, sniffing out things that shouldn't be there. "He's trained in narcotics," a deputy said. "He'll pick up on cocaine, heroin, methamphetamine, MDMA, marijuana, and cell phones." Nothing but memories remain after Dolar was said to have died during a training session Thursday. While his cause of death is unknown right now, the sheriff's office says an investigation is underway. They add, K-9 Dolar was very playful, but excelled at his duty. In a statement, Sheriff Chris Amason called the loss devastating. Not only was he a remarkable working dog, but he was also a beloved member of our family. His contributions to our department and the community will never be forgotten. Sheriff Amason News 4 will be following the investigation. The sheriff's office says it will release details on a memorial service soon.