Sgt. Tom Lovejoy pulled his keys out of the ignition of the squad vehicle and stepped away. A dog was still in the back of the vehicle, panting.

What followed got the Chandler police officer into a world of trouble in August when he forgot his K-9 partner, Bandit, inside the vehicle, leaving the dog to die in the summer heat.

On Wednesday, however, when he repeated those actions, something was different. The engine and air conditioner remained on, even though the key was not in the ignition.

VIDEO: Lovejoy talks about fallen K-9 and his new pet safety invention

Lovejoy has been under intense public scrutiny and is facing a criminal charge of reckless animal abuse for what happened in August. But since then, out of the public eye, Lovejoy has worked on an invention he hopes will stop others from being in his situation.

It is essentially a large black mat, installed in the back of a vehicle and electronically connected to the engine. If a dog is on the mat, the engine will not shut off.

“There’s a lot of times that you get caught up in life and you forget something’s there,” Lovejoy said Wednesday during a demonstration of the invention.

This, he hopes, would change that.

It was a somewhat emotional day for the former head of the department’s K-9 unit.

The vehicle he used for the demonstration was the same blue-and-white sport utility vehicle Bandit died in. The dog used in the demonstration, a Belgian Malinois named Beth, is Bandit’s breed.

“There’s a lot of little things in here that remind me of him,” Lovejoy said.

Still, over and over, in front of television cameras and reporters, Lovejoy showed how it could prevent a death. During interviews, he often stopped short of using the phrase “Bandit’s death.”

“This is part of the grieving process,” he said. “That’s basically the driving force behind this. I don’t want anybody to go through what I’ve been through in the last two months.”

Lovejoy partnered on the invention with Brian Shackelford, a K-9 handler for the Glendale Police Department who is also an inventor. The two began talking about creating this device when Shackelford called Lovejoy to extend his condolences.

“We talked it over and discussed the lack of anything in the market that would prevent something like this from happening,” Shackelford said.

The result is called Ocu-Alert, and Shackelford hopes to sell it to police agencies and civilians alike for about $800. He said it has cost more than $3,000 to develop.

Of the eventual sale price, Lovejoy said he will not take a penny.

“He has a certain amount of guilt over what has occurred, and this is his way of dealing with that,” said Shackelford. “In his heart, he wants to give back.”

Wednesday’s demonstration came in the middle of the first full week Lovejoy was allowed to speak publicly about his situation. He was previously under investigation by his own department and said the department had not allowed him to speak.

On Friday, however, the results of the investigation were released and he has been giving regular interviews about the incident, trying to repair his public image, though he says his lawyer advised him not to talk about the case.

The Chandler investigation released last week found Lovejoy acted negligently in Bandit’s death, and not recklessly, as Maricopa County law enforcement says he did.

The distinction is an important one as there is no law against negligent animal abuse in Arizona, only reckless abuse, a misdemeanor.

Lovejoy has pleaded not guilty last month to that charge. He is scheduled to go to trial Jan. 10.

Tribune writer Mike Branom contributed to this report.