ARNOLD, Mo. — An Arnold Police Department’s K-9 officer, named Vader, died yesterday from heat exhaustion.

The police department says that the K-9’s handler left Vader in a running patrol vehicle with air conditioning. When the handler returned to the vehicle, the air conditioning system had malfunctioned and the heat alarm system failed to activate.

The dog was rushed to two veterinarian clinics for treatment, but succumbed to his injuries. Vader was four years old.

“All Arnold Police Department K-9 vehicles are equipped with a system that notifies the handler by phone, activates the emergency lights and siren, sounds the vehicle horn, activates cooling fans, and rolls down the vehicle windows, if the vehicle temperature increases to a certain level. In this instance, the heat alarm system failed to activate,” the police department’s Facebook post states.

The department is investigating the incident.