The first-ever body cam footage from the Nye County Sheriff's Office captured a disturbing scene that one man says changed his life and eroded his trust in police.

Contact 13 Chief Investigator Darcy Spears has the exclusive story about a dog's violent death at the hands of a deputy.

Gary Miller will always remember his pit bull, Blu, as ready to play with a toy or receive a treat, perhaps even a belly rub.

The world-record holding power lifter and certified firefighter is a true strong man. But even he can't hold back tears when it comes to his beloved pet.

"I look for him every morning when I walk out," said Miller as a tear ran down his cheek.

Gary's family rescued Blu when he was just a puppy and he'd been with them for almost six years until April 10, when a Nye County Sheriff's deputy went to Miller's Pahrump home after his security company reported multiple panic alarms.

On the body cam footage, we can listen in as Deputy John Tolle talks about other motorists while he races to the scene.

"Oh, you're an idiot, aren't you?! I mean, you're just a new kind of stupid," Tolle says as he battles traffic.

Arriving alone at Miller's home, he unlocks the gate and enters the property. As he walks toward the door, Blu begins to bark from behind the house.

Before Tolle sees the dog, he starts talking to himself, saying, "Oh, don't be mean. Don't be vicious."

He knocks on the door as Blu continues to bark and comes around the corner of the house.

Deputy Tolle continues talking softly as Blu approaches, saying "Oh, don't do it, doggy. Don't do it, doggy. Stop it. Stop it."

He then shoots the dog once from approximately 10 feet away and continues firing three more times as Blu falls off the concrete path into the weeds.

Twelve seconds pass from the first bark to the first gunshot as Gary is on his way to answer the door.

Body cam footage:

Gary Miller: Hey!

Dep. John Tolle: Let me see your hands, man!

Miller: Did you shoot my dog?

Dep. Tolle: He just attacked me!

Miller: You shot my dog?!

Dep. Tolle: He's attacking me!

We showed the body cam video to Gina Greisen with Nevada Voters for Animals.

"That was completely unjustified! He's running up to see what's going on. It's his property. That's his property! But he's not even doing it in an aggressive running manner. He's jogging up to the front. I'm horrified by this video!"

The press release sent out by the sheriff's office after the shooting supports Deputy Tolle's account.

It says the dog "charged the deputy, attempted to attack him" and posed an "evolving threat" from an "aggressive animal."

"Blame the victim!" said Greisen. "We're sick and tired of it! The public is tired of it! Whether it's a person or an animal, stop blaming the victim and stop circling the wagons! The public wants the truth!"

And so did Nye County Sheriff Sharon Wehrly, who opened an internal investigation.

"I don't take the death of pets lightly," Sheriff Wehrly said. "When I was first told about the shooting, I was told by a detective that it was totally and completely, irrevocably justified. I'm very, very glad that that body cam was there."

Here's more from the body cam:

Deputy Tolle: The dog came after me!

Gary Miller: The dog was coming up TO you!

Dep. Tolle: Well, he was barking and growling like he was coming to bite me.

In an interview with Contact 13, Miller said, "If the dog's wagging his tail, even if he's barking and growling, he's no threat. My dog was still wagging his tail when he was laying on the ground bleeding to death."

Darcy Spears: Was this an appropriate use of force or did this deputy go too far?

Sheriff Wehrly: Well, you know, that's hard to say.

Sheriff Wehrly says two recent pit bull attacks, one deadly, created a climate of fear.

"At the time, he was scared. He had a gun in his hand. And, and he used it."

"Because he was scared?!" Miller said incredulously. "I mean that's ridiculous. To me, the man has no control. If he's got no self-control, he's got no business having a badge and a gun."

Making matters worse, the silent signals sent by the remote on Gary's key fob turned out to be false alarms.

Sheriff: He had been sitting on the panic button. But no one knew that.

Darcy: He tells us that the alarm company notified the sheriff's office that it was a false alarm.

Sheriff: I checked that. There was no record.

The alarm company has a record.

We obtained the activity report from Pahrump Central Security, which shows they contacted the sheriff's office and notified a dispatcher named Ashley about the false alarms.

Contact 13 confirmed the alarm company's notes say that Ashley advised the deputy was still en route, but he'd be updated.

Deputy Tolle on body cam: "He said he called the alarm company and canceled it, but we never got a cancellation. We got just the alarm, so..."

And because of that, Sheriff Wehrly says Tolle didn't use the procedure he was trained to follow.

Sheriff: Generally what we'll do is bang on the gate or make some kind of noise to see if there's a dog on the property. But because of this type of call, that didn't happen.

Darcy: Has anybody ever been out to that property for any reason before? Did they know there was a dog there?

Sheriff: No, the property isn't marked that there's a dog inside.

But the Sheriff's office confirmed police had been to Miller's property about a dozen times over the last five years.

On the body cam video, Tolle talks to a sergeant, who showed up after the dog was shot

Sergeant on body cam: I've been out here with this guy before.

Dep. Tolle: Have you?

Sgt.: Kind of an asshole sometimes.

Dep. Tolle: Especially when I shoot his dog.

Sgt: Even more so.

Gary says that callous attitude continued after Blu passed away.

"Ask them why they cremated the body of the dog without contacting me. Without getting consent from me."

When Contact 13 started asking those questions, this story took a very strange twist.

And our findings sparked a new internal investigation at the sheriff's office. We'll bring you those findings in part 2 of this story which airs on Monday.

The raw video from the body camera is below. Warning: contains graphic content and language. Video courtesy of Nye County Sheriff's Office.