QUINLAN, Texas (CBSDFW.COM) – The Hunt County Sheriff’s Department is investigating what appears to be a disturbing case of animal cruelty.

A teenager’s heart is broken after what happened outside her home in Quinlan Sunday morning.

Journey was a 4-year-old golden retriever specially trained to detect the smell when Hannah Westmoreland’s blood sugar was low.

The town of Quinlan raised $10,000 to get a service dog for the young girl with diabetes who’s now 15.

For nearly four years, Journey has been a playful family member and right by the side of Hannah, ready to alert her.

On Sunday morning, Journey was let out for his daily quick dip in the pond he loved outside his family’s rural home.

That’s when someone shot the service dog while his family was inside.

Journey died despite efforts by a vet clinic to save him.

The family has no idea who did it or why.

“He took Hannah’s little hero for no reason,” said Hannah’s mother, Tina Westmoreland. “He took what has saved her life more than once. She’s about to get her drivers license and he was going to protect and he was going to be with her while she was in college to keep her help healthy in college.”

“He was my best friend,” said Hannah.

The vet did preserve the bullet removed from the dog.

There is a Justice4Journey Facebook page for messages, tips or a place for someone to help fund a reward.