Police officers are trained to be handlers of police dogs. They learn the proper knowledge on how to work efficiently with these dogs. Leaving a dog in a hot patrol car is just plain negligence. The way you will not leave a baby inside a hot car, the same applies to an animal.
The police officer should have resigned after the K-9 died in his patrol car. Leaving an animal in a hot patrol car is a serious error in judgement, as well as gross negligence while on the job. A policeman that exercises such poor judgement should not be responsible for the safety of a suspect in his patrol car. In short, a policeman that leaves a K-9 in a hot patrol car should no be working in law enforcement.
The tragic story of a K-9 dog dying in a patrol car raises the question of whether or not the police officer responsible should be kept on the force. I don't think he should: if animal cruelty is no big deal, then who knows what horrific acts he may commit on humans?
If the death of the dog in the K-9 patrol car was the responsibility of the officer involved then yes he should resign because obviously he can not take care of his fellow officer and let them die because they were incompetent. Animals can not take care of themselves when humans keep them down.