The dog's owners believe their pit bull should never have been shot.
The officer was given a letter of reprimand for shooting that dog, according to an internal investigation. It also says the officer should have done more to investigate before opening fire.
The officer told investigators he believed the pit bull could have turned on someone else, and that is why he opened fire. Two officers were called to the scene after two pit bulls started fighting each other in a fenced enclosure.
A witness told police the dogs were fighting for about 20 minutes, both were bloody and wouldn't stop.
The officers claim they didn't know the yard was completely fenced in, and they saw a person standing in the yard.
One of the officers used a baton to get the dogs to stop fighting, but when that didn't work the other opened fire.
The family involved filed a notice of claim with the city, asking for $300,000 in damages.
"Do we want anybody, let alone police officers coming onto our property and shooting our dogs through a chain link fence... it's tough to lose a family pet, and they have four dogs, but obviously losing any dog would be hard," said attorney John Torgenson.
Chandler Police say they have completed a full investigation, but have declined comment because of the pending legal issues.