A beloved family pet was found dead in a stolen minivan late Monday, apparently overcome by heat after she and the vehicle were abandoned with the windows closed, police said.

The minivan had been stolen Saturday in front of a shop in Studio City after Nayo Mateo left the vehicle running with Maru the golden Labrador retriever inside while he ducked inside to ask his wife to finish her shopping.

Detectives with the Los Angeles Police Department's North Hollywood division said they received a call 4:30 p.m. Monday of an abandoned car in Studio City.

Officers found Maru dead inside. The Honda Odyssey was impounded by the LAPD and is being tested and analyzed, a detective said.

"The preliminary finding is that the dog passed away from heat stroke," said Detective Larry Burns, with the North Hollywood auto theft unit. Monday's temperature in Studio City reached 88 degrees at 4 p.m.

The minivan and Maru belonged to the Mateo family of South Los Angeles. Nayo Mateo said he was waiting in the vehicle Saturday with Maru dozing in the back while his wife was shopping at a children's clothing store on Ventura Boulevard. When he went in to find his wife, he said, he left the keys in the ignition so that the air conditioning would stay on for the dog.

"I didn't even go all the way inside the store," he said in an earlier interview. "It was 10 seconds, and the car was gone."

The panicked Mateo ran to a nearby pet shop to ask if they had a surveillance camera. Sheilah Aragon, who runs the rescue group Mutt Match L.A., happened to be inside holding an adoption clinic. She helped organize a $2,000 reward and get the information posted on Facebook and CraigsList.

On Tuesday, Aragon said she was heartbroken.

"Obviously, Nayo and his family are devastated," she said. "The cruel irony is, he thought he was doing the right thing by leaving her in the car with the AC on, in the end having the windows rolled up is what killed her."

"I am sad, heartbroken and very disheartened by our cruel world," she added.

Staff Writer Kelly Goff contributed to this report.