By Roseanne Tellez

(CBS) — A sad loss for police at the Cook County Forest Preserve: a K-9 died earlier this month after being found in a hot vehicle. But as CBS 2’s Roseanne Tellez reports, that’s only part of the story.

Drago the dog was remembered on an Oak Forest Police Dog memorial page. His police career ended tragically, after three years, in a hot car in the parking lot at the Oak Forest Police Department.

His officer took a suspect inside. Temperatures hit 90 degrees. When Drago was found, the fire department responded to the call.

dog1 Police Dog Dies From Heat Exposure

(Cook County Forest Preserves Police/Facebook)

First-responders tried a variety of measures to try to revive the dog, Oak Forest Fire Chief Pat Duffy says. But Drago never recovered.

“We are heartbroken to lose a canine member of the Forest Preserves of Cook County Police Department,” the police agency said in a statement. “The protection of wildlife and living things are at the core of our mission and we take this loss very seriously.”

The forest preserve confirms the police vehicle had a special Temperature Monitoring Alert System, designed for especially for police dogs. They’re now investigating what went wrong on the day of the tragedy, June 14.

Fire Chief Duffy says the loss was upsetting to his firefighters, but added, “They know they did the best they could, given the circumstances.”

People for the Ethical Treatment of Animals said in a statement that their heart goes out to the Forest Preserve Police. The group says 12 police K-9s died in hot cars last year. They urge all departments to invest in warning systems.

The officer involved is still on the job but not working with K-9s, pending the end of the investigation.