The deputy argued that the dog, Candy, threatened his safety.
Candy's owner, Cole Middleton, is a third generation dairy farmer. After Candy died, Middleton began a campaign on Facebook that is getting national attention and said she was killed for no good reason.
Last week, someone broke into Middleton's house. He was on his tractor when the deputy arrived to investigate.
Middleton could see Candy in the bed of his truck, and when the deputy walked up to the house, Candy jumped down. She was barking, and then Middleton lost sight of her.
"The officer comes down and says, ‘Sir, I'm sorry, I shot your dog -- she charged me,'" said Middleton. "I became very hysterical and very upset…I said, ‘No, no, no…you shot my baby.'"
Candy was more than just a pet to Middleton -- the 2-year-old Blue Heeler was his work partner, always by his side.
After the shooting, the deputy called for backup, and Middleton pulled out his phone and started recording.
"What I'm saying is the man pulls up without cause and shoots my dog," Middleton can be heard saying in the video.
"Your dog charged me, buddy," the deputy says.
"No, no," says Middleton.
"I got it on dash cam man; your dog charged me," says the deputy.
Wednesday morning, the sheriff let Middleton watch the dash cam footage from the incident. He says it doesn't show Candy charge the deputy.
Middleton had Candy's body examined by a veterinarian. The findings "suggest Candy was shot while retreating from the shooter."
Sheriff David Traylor told FOX 4 he regrets what happened. An investigation into the incident is ongoing.