GAINESVILLE, Ga. -- A former Gainesville police officer is accused of doing the unthinkable to a police dog he was training.

The Georgia Bureau of Investigation is looking into claims that the officer tied an electric collar to the dog’s genitals as a way of teaching it not to bite.

Gainesville police chief Frank Hooper told Channel 2 Action News reporter Tom Jones that it came as a shock to him when he learned one of his officers was accused of abusing the dog named Diego.

Hooper said Diego was so vicious, possibly from prior military training, that he had to be euthanized.

Hooper said he didn’t know if the alleged abuse played a role in the dog's death. He said the investigation will determine that.

The officer, whose name is being withheld by Channel 2 Action News because he hasn’t been charged, suddenly resigned as an investigation into his handling of Diego got under way, said Hooper.

“We look at our canines as part of our department, part of our agency,” said Hooper.

Jones spoke with the accused officer, who denied abusing Diego.