An internal investigation into the matter was conducted by supervisors of the Mills Police Department and appropriate disciplinary action was taken, according to the release. Officer Miller has been charged with misdemeanor animal cruelty as a result of the death of Nyx, K2TV reported.
Police said the investigation is now being turned over to the Wyoming Division of Criminal Investigation.
The Mills Police Department has suspended its K-9 program while it reviews the policies that allow K-9 officers to be training officers, according to the release. The department is also considering preventive equipment such as heat alarms in the vehicles.
Officer Miller has been with the Mills Police Department for more than 4 years and was named Police Officer of the year for 2013, according to department.
Watch a video report on Nyx's death by ABC affiliate K2TV in Casper: