The boy, identified as John Bruno, passed away Saturday at Children's Hospital of Philadelphia, police say.
Last Wednesday, Bruno was playing outside with the 18-month-old hound, which was not uncommon, according to family.
Bruno's mother told police she looked out the window and saw him laying face-down in the snow. The dog was tugging at the scarf around the boy's neck, according to police.
The mother ran out of the house and found Bruno unconscious and unresponsive.
She untied the scarf, which police say was tight around her son's neck, carried him into the house, and immediately called 911.
Arriving paramedics performed CPR on the boy before transporting him to the hospital.
The child's parents and older sister were at home at the time of the incident.
The Philadelphia Medical Examiner's Office will release an official cause of death.
Police say this appears to be a tragic accident, but their investigation continues.
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