DAYTON, Ohio (AP) — The death of a 7-month-old Indiana boy who was attacked and killed by a dog in Ohio has been ruled an accident.

The Montgomery County coroner’s office says in its preliminary findings from Monday’s autopsy that Jonathon Quarles Jr., of Indianapolis, died of blunt force injuries. Police say his step-grandmother was watching him for the day when her dog attacked and killed him Sunday.

Police Lt. Wendy Stiver says the dog was removed by an animal control officer and was being held Monday. Authorities say it was unclear why the dog attacked and are investigating.

Police say the dog registered at the step-grandmother’s address was identified as an American Staffordshire terrier.

A June police report shows a dog registered at that address allegedly attacked and injured another dog.