The Humane Society of North Texas is making changes to its protocols after a pit bull mix attacked a smaller dog—leaving it bloodied and needing a veterinarian.

KELLER, Texas --The Humane Society of North Texas is making changes to its protocols after a pit bull mix attacked a smaller dog—leaving it bloodied and needing a veterinarian.

The attack happened Saturday morning just before the Keller Regional Adoption Center opened. The property is owned by the city but is operated by the Humane Society.

Glen Bulawka was visiting the shelter and filmed the attack with his cell phone.

“I normally come here in the morning to drink my coffee, and watch the dogs in the play yard,” Bulawka said. “We adopted our dog from here, and my kids volunteer at the Humane Society.”

“I thought it was kind of odd that this little guy was getting picked on so much, and within two seconds this pit bull grabbed onto its neck and just kept holding on,” he said.

In the video, you can see the pit bull with its jaws around the neck of a small Chihuahua. As the video continues, the pit bull can be seen repositioning itself and grabbing the neck of the dog repeatedly.

At one point, it drags the tiny dog across the play yard—which is visible to the public but inaccessible with a tall fortified fence.

No workers can be seen anywhere as Bulawka yells for the dog to get off the Chihuahua.

Before he began filming, Bulawka said he tried to get the attention of any employees inside the shelter by banging on its doors—but no luck.

He called 911 before hitting record. “I started filming because I felt like this was neglect,” Bulawka said.

A police officer eventually made it to the scene, and the dogs were separated. Keller Police is adjacent to the shelter and the officer could gain access to the building.

The Chihuahua, whose name is Taco, was taken to a veterinarian and survived the attack.

The pit bull, whose name is Amber, is now in quarantine—according to the Humane Society.

Still—Bulawka had a lot of questions, like why a small dog would be allowed to play with larger dogs in an open area with no one watching.

A spokesperson for the Humane Society of North Texas says an employee let a group of dogs out to play and left them unattended.

“That wasn’t playtime,” Bulawka said. “That was an aggressive dog—that’s what I thought.”

Both Taco and the pit bull came in about a week ago, the Humane Society said, and have played together before with no issues.

But Spokesperson Cassie Lackey said that the video has sparked a change in protocols. From now on, groups of dogs will no longer be allowed to play together unless an employee or volunteer is present at all times.

“There was a mistake made, absolutely, and again their well-being and care is our utmost concern,” Lackey said. “When we know better we do better, so that’s what we’re going to do.”

Taco is now being fostered as he recovers, and will be up for adoption starting Saturday.

Lackey says that Amber could be adopted out if it doesn't show any further behavioral issues.