WASHINGTON — (CNN) A Henderson family is trying to figure out how their dog, a 9-year-old Shih Tzu named Mr. Chops, was left in an animal control van overnight, resulting in the dog’s death.

The Whipple family said they adopted Mr. Chops from an abusive family about seven years ago, and since then he had become a member of the family.

“He was always up and trying to play with people,” Brandon Whipple said. “I still feel like he’s kind of here, and I can’t really imagine that he’s gone yet.”

On Thursday, Mr. Chops got out of the house and was found by a neighbor.

“I was worried. Me and my dad immediately got into the car and we drove around for at least an hour or two,” Whipple said.

The neighbor brought the dog to a veterinarian, who read Mr. Chops microchip and called Henderson Animal Control to help return the dog to the Whipple family.

But instead of bringing the dog into the shelter, where the family could pick him up, the animal control officer forgot about the dog and unintentionally left Mr. Chops inside the hot animal control van overnight.

Officers found the dog’s body the next morning, 17 hours after he had been picked up.

“All I can imagine is, it must have been the absolute worst way to die for a dog,” Whipple said. “To be left in a car, to be actually be cooked to death, I imagine he would have tried to claw his way out or something.”

The Henderson Police Department oversees the city’s animal control department and said the officer who picked up the dog unintentionally left him in the van.

“The officer placed it in his truck, went on a couple more calls, and went back to the shelter,” Deputy Police Chief Jeffery Stilson said. “At 4:30 in the afternoon, he secured for the night and went home.”

Stilson said the department is now investigating the incident and changing policies to make sure something like this doesn’t happen again.

Starting on Monday, all animal control vans will be inspected at the end of a shift, and officers have to return to the shelter immediately after a pick-up unless there is an emergency.

The Whipples see the changes as a good thing, and they hope this doesn’t happen to any other family.

But Whipple also wants the animal control officer responsible for Mr. Chop’s death held accountable.

“I want him fired. It’s not an OK thing to have happen. It’s a life,” he said.

The Henderson Police Department would not disclose if the officer involved has been fired or is facing any discipline.

This is the first time an animal has been killed in a hot car while in Henderson Animal Control custody.