“... I would think they would train them not to attack police officers?”
I know a K-9 officer in my county and this is what he told me. When a dog is “on duty” and “working”... he has to be handled by the trainer at all times. In fact, the radio will announce to the officers on a scene that k-9 is out of the car. He said you will see cops jump right back into their cars. Apparently, K-9 dogs cannot distinguish between law enforcement and other civilians (who may be wearing uniforms). Dogs see in black and white and apparently to distinguish between a cop’s uniform and someone else’s is difficult if not impossible. From what he told me, a K-9 dog accidentally biting another officer is not uncommon. They are supposedly trained to ball up and the handler is suppose to give the command to release.
Most other carriers are not pleased. Some won't even stop by the house.