The Gander SPCA is investigating what it calls a horrific discovery — a dog tied to a rock and thrown into a river.

The group retrieved the medium-sized, brown and black male dog from the Terra Nova River Thursday afternoon.

A young boy and his mother found the dead animal.

The SPCA's Betty Suley says the dog was tied to a 5.5-kilogram rock and thrown into the river.

'This was definitely intentional. The dog had the rope tied around his neck and the rope was tied around the rock ... It was no way this could be an accident.'—Betty Suley

"This was definitely intentional,” she told CBC News. “The dog had the rope tied around his neck and the rope was tied around the rock ... It was no way this could be an accident."

Suley says the dog's body was bloated, and could have been there for weeks.

“This dog had to suffer, and suffer a lot,” Suley said.

The dog's body was hard to retrieve. A cabin owner used his boat to help authorities bring it to shore.

“The rope around his neck was extremely tight,” Suley said. “I guess this was from the dog struggling, because there's no way he could have gotten up once he was thrown over."

The provincial veterinarian’s office will perform an autopsy.

The RCMP confirms it's also investigating the case.