Gavin Wright can't explain what happened.

He said Thursday that his 3-year-old American pit bull terrier, Achilles, whom he had owned since the dog was a pup, had never displayed any type of aggression.

The pet, he said, was even more attached to his 74-year-old father, Cliff Wright, with whom Gavin lived on Santa Fe's northeast side.

"He loved the breed, he loved the dog," the son said in a phone interview Thursday. "He loved Achilles."

However, when Gavin Wright came home about 7 p.m. Wednesday, he found his father lying motionless on the front lawn.

Police say the dog had killed him.

Lt. Louis Carlos said a preliminary finding by the state Office of the Medical Investigator is that "the injuries sustained by Mr. Wright were from the dog. There were no other medical reasons related to his death."

According to Carlos, the elder Wright apparently had been watering the lawn that evening at the home at 211 Williams St., just across Bishops Lodge Road from Fort Marcy Park. The hose was still running when police arrived at the scene after receiving a frantic phone call from the younger Wright.

"We do not know what precipitated the attack," Carlos said.

Gavin Wright said Thursday, "I'm still overwhelmed and shocked. There was never anything leading up to this."

He said Achilles had been his dad's daily companion, his guard dog and his best friend.

Cliff Wright was retired. He had owned a pawn shop on Read Street called The Hock Shop. His son works as an auto technician and was away from the house all day.

Police released a past report concerning an encounter in 2005 between Cliff Wright and another male pit bull on the property in which the elder Wright had been bitten.

As of this week, police reported, the family had three dogs, two of which were pit bulls terriers.

The New Mexican published a story about the Wright family in 2002, when Gavin Wright was a football player at Santa Fe High School. The story explored the relationship between him and his mother, who passed away after an apparent electrical accident in her home when he was 17.

Now 27, Gavin Wright is dealing with another sudden tragedy.

Cliff Wright also is survived by a daughter, Karen Wright.

After the grisly attack, Santa Fe Animal Control officers on Wednesday night quarantined Achilles. Carlos said the animal will have to be put down.

Carlos said the Police Department will ask Gavin Wright to agree to voluntarily have the dog euthanized. If he refuses, police will take the matter before a judge.

Gavin Wright, after a brief silence over the phone, said he had "no idea" what he was going to do about Achilles.

Contact Nico Roesler at 986-3089 or nroesler@sfnewmexican.com. Follow him on Twitter @nicoroesler.