A Calgary family has made the difficult decision to euthanize their pet dog after it attacked a seven-year-old boy.

Joshua Peech was at a friend's house on Saturday morning when he was attacked by the English Mastiff.

The 150 lb dog Hurley lashed out when he was accidentally hit by a door.

"He bit me and I was swung around like a rag doll," says Peech.

Peech was taken to hospital where he received three dozen stitches to his shoulder. The attack also meant surgery for the seven-year-old to fix his broken collar bone.

Kim Singh, who owns Hurley, is devastated about the attack which her children also witnessed. "I am looking at this as an unfortunate, tragic event – an accident, a true accident – that happened."

The three-year-old Mastiff is now at Animal Services.

He was supposed to go through a dangerous dog hearing but Singh isn't willing to take any chances and has opted to have the dog euthanized.

"I felt that I should put the dog down. I could not live with myself that perhaps if my dog gets startled again, by my own kids or someone else, he could do this again," says Singh.

The family says Hurley has never shown aggressive behaviour before.