BOSTON (MyFoxBoston.com) -- An East Boston family is mourning the death of their pet killed by another dog and a criminal investigation is now underway.
Four-year-old Mia, a 7-pound Yorkshire terrier, was the apple of her family's eye.
"It's just, I'm loss without her, she was my best friend," her owner said.
Mia was out for a walk with her owner Monday when suddenly it all went wrong.
"I was walking Mia to put her back in the car and I turned around and I see all the dogs coming at us," Mia's owner said.
A group of four dogs were out with a walker, three of them unleashed.
"In my mind I didn't think they were gonna do anything I should've picked her up fast," Mia's owner said.
That's when a large bull-mastiff attacked.
"The bull-mastiff came right there and got her on the side, picked her up, was shaking it's head," she said. "I was trying to open his mouth."
The walker runs the Walk-a-Lu dog walking company, and is now criminally charged. The walker did not want her face shown on camera but told us it was all just a terrible accident.
"It's heartbreaking and I am a dog lover," she said. "And I never would've wanted his dog to be hurt."
She went on to say it was a "poor decision" on her part to keep the dogs off leash.
And Mia's owners in mourning want to make sure it never happens again.
According to an incident report, there's a complaint to be filed in East Boston District Court against the dog walker for animal cruelty. The dog involved is being quarantined and under observation.