Police had to shoot dead the animal, reported to be an American bulldog, so that paramedics could enter the terrace house where the boy was savaged.
The young victim, named locally as Luca, whispered “I’m going to die aren’t I?” as he lay injured after dragging himself upstairs to avoid the dog.
The teenager had to play dead to prevent further attacks and a neighbour, Dean Crowe, had to hit the dog with a shovel at the end-of-terrace house in Little Horton, Bradford.
Luca was yesterday said to be stable at Leeds General Infirmary after undergoing surgery to his face, shoulder, torso and hip.
The homeowner, who gave her name only as Rachel, said the teenager had been teasing the dog, Patch, and getting it “worked up” by throwing seeds at him prior to the attack on Sunday evening.
She said she had been given the dog two days earlier and had kept the animal outside with her other dogs Coco, a Great Dane, and Demon, a Rottweiler puppy.
Rachel said: “I was in the bathroom and I heard Luca jumping around in the bedroom with Patch – teasing him. The next thing Luca was screaming and Patch had grabbed him and pulled him down the stairs and into the kitchen.
“Patch was ripping into Luca. He bit his hips and side, his shoulder and face – Luca’s ear was hanging off.”
Neighbour Mr Crowe, 42, heard the screaming and barking and came to Luca’s aid, hitting the dog with a shovel and kicking it in the testicles, but the dog would not stop until it thought the teenager was dead.
Rachel said: “Every time Luca moved an inch Patch attacked him again. Only by playing dead could he stop being bitten.
“While Dean was hitting and distracting Patch, Luca managed to drag himself upstairs.
“He was in and out of consciousness. There was blood everywhere and you could see the inside of his neck. Luca kept saying ‘I’m going to die aren’t I?’.”
Mr Crowe stayed inside and warned police not to enter. Firearms officers smashed a pane of glass in the front door and shot Patch from outside.
He said: “The dog was attacking the lad’s face when I saw it. I just ran in with a shovel and kept hitting the dog.
“I’ll never forget the lad’s last words to me, ‘I’m going to die, I’m going to die’. It’s a horrible thing to have to see and hear.
“I just pray the little lad pulls through, but his face was a mess.”
Rachel said Patch had been described as “timid” by the person who had given the dog to her last Friday.
American bulldogs are not on the list of animals banned in the UK under the 1991 Dangerous Dogs Act.
Her dogs are normally chained up in the yard, but were allowed to roam free on Sunday evening when Luca came to visit. The teenager left the front door open and Patch wandered into the house.
Rachel said: “Patch was described as soft to me and had been a family pet and good with children, but was unwanted, so I took him in.”
Katrina Green, who lives near to where Sunday’s attack took place, said she heard sirens and other commotion in the street and did not know what was happening.
“We thought it was a murder at first,” she said, “or that it was a fight. I’m really shocked. It’s not the dog’s fault, it’s how they bring them up.”
Police said they were called to an address in Frank Street at 7.26pm and confirmed they had to shoot the animal so paramedics could attend to the boy.
A West Yorkshire Police spokesman said: “Inquiries are now ongoing as to the breed of the dog and to establish whether any criminal offence has been committed.”
The attack is the second incident this month of a dog inflicting serious injuries on a child in the region. On August 6 a two-year-old girl needed hospital treatment when she was attacked by a Rottweiler in Rotherham.
The owners of killer dogs could face life in prison if an online petition garners enough public support, as part of plans to change the 1991 Dangerous Dog Act announced by the Government earlier this month.
The proposals could lead to a significant jump from the current maximum jail sentence of two years to up to life imprisonment.
Sixteen people have been killed by dangerous dogs since 2005.