A retired K9 unit from the Celina Police Department has died from natural causes.

K9 officer Nick served the department for ten years, starting in 2000 as the department’s first K9 unit, according to a release. The majority of K9 officers serve for five to 10 years.

During his ten year career, his search and tracking abilities led to dozens of apprehensions, according to the release. In the last three months of his career, Nick served as a mentor to his K9 replacement Ted. Ted learned social skills and a love of children from Nick, police said.

Nick was less active during retirement and showed signs of fatigue in the last couple days. He passed away in his sleep early Wednesday morning.

He lived with his former handler as a family pet until his death.