Deputies found Miller dead with his face beaten and his eye swollen, but there were no other apparent injuries to his body, the television station reported. According to an arrest affidavit, Nealey had injuries on his face and his right hand was swollen and red.
Original report: Miller and Nealey were in Florida for a law enforcement conference, KOKI reported.
Authorities said the event is the Southeast Public Safety Training Conference, WEAR-TV reported.
The City of Mannford posted a statement on Facebook, writing that Miller was married with three children.
"We are heartbroken by the news," Mayor Tyler Buttram said on Facebook. "Please keep both families in your prayers as we work to move forward."
Mannford Town Administrator Gerald Haury named Jerry Ridley as interim police chief, according to the city's Facebook post.
Nealey will appear before a judge in Escambia County on Tuesday, WEAR reported.