Officials said a 2-year-old dog, a neutered male American Staffordshire terrier-mix named Polo, mauled a 3-day-old boy to death at his family's home in San Diego on April 21, 2016.

EMBED >More News Videos According to police, the mother opened a door after she left the baby on the couch and walked away thinking the dogs were tied up. Moments later, she heard her baby's cries.

SAN MARCOS, TX (KTRK) -- Police are investigating after a dog mauled a two-month-old baby to death Tuesday in San Marcos.Right now, investigators say this all appears to be a tragic accident.The family who owned the dog told police they have had the dog for eight years, since it was a puppy.During that time, the dog allegedly never showed any signs of aggression.Sadly, however, the victim's father found two-month-old Skylar Dean Julius covered in bite marks Tuesday and called 911.Cdr. Kelly Earnest with the San Marcos Police Department said the child's father had fallen asleep after the baby girl began taking a nap in her infant bouncer.But when he awoke, he found little Skylar's body. She appeared to have been mauled to death by the dog.Evan Kokenzie is a neighbor of the family, and said he came around the corner of his home to find three cop cars and a big commotion."I saw a big dog in the back that was barking and scratching at the door," Kokenzie said. "It was a big, like a reddish German Shepherd-looking dog."Child protective services is also investigating the child's death."This is something that is so tragic for both family and a pet lover or pet owner," Earnest said. "You don't really know what animals will do.""I don't think that this family had any idea of what their dog was capable of."