Police in the south Texas town of San Juan await test results on bones found in a backyard shed.
Preliminary investigation suggests at least some were human and purchased on the Internet for ceremonial purposes.
San Juan Police Chief Juan Gonzalez says police also recovered bones from at least three dogs.
Gonzalez said authorities were initially concerned because a police badge was recovered near a blood-soaked shrine in the backyard.
Gonzalez says the former officer says the badge was stolen from him years earlier.
The site was initially found when the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives served an arrest warrant at the home Wednesday morning.
U.S. Attorney's Office spokeswoman Angela Dodge says Ruben Ambrosio Fonseca was arrested on a charge of being felon in possession of a firearm Wednesday.