Jade Hodgson, 19, and sister Carla, 16, desperately tried to pull Buster - a STAFFORDSHIRE/PIT BULL CROSS - away as it went for their father Stephen's throat.
But the dog was too strong for them and its powerful jaws ripped into Stephen's jugular.
(The Staffie-pitbull cross, called Buster, was tasered by police and later destroyed)
He died from a heart attack triggered by massive blood loss.
His devastated family paid tribute to the dad-of-three yesterday as his kids described him as their "best mate".
Stephen, an unemployed carpenter, had been watching Prison Break with his daughters on TV, all three of them sitting on a bed in an upstairs room on Sunday afternoon.
He had been suffering from a pre-existing medical condition - thought to be a liver problem - and suddenly fell ill.
He slumped over the side of the bed, startling three-year-old Buster, one of four dogs the family owned.
Buster began barking so the girls ushered him into the garden of their semi while they tended to their dad.
Jade said: "I was trying to look after dad and lift him back up onto the bed but as I was trying to do that Buster came back in and ran up the stairs.
"We didn't want him in the room because he was getting excited and barking but he barged open the door. He's a big, strong, heavy dog and we couldn't keep him out.
"He saw my dad leaning over the edge of the bed and he went for him, there was nothing we could do."
Carla added: "Buster was biting dad's throat and there was suddenly a lot of blood. We were doing anything we could to get him off. He didn't have a collar on to hold onto so we were just pulling him.
"I had hold of his back legs and was trying to drag him off but he was just too strong.
"We knew things were really bad for dad, he might have gone before the emergency services even arrived.
"It was horrific and we won't be able to forget it, but I'm glad we were there for dad to try to help him. At least we know that we did everything we possibly could to try to save him.
"We wrapped a sheet around his neck to try to stop the blood but he was bleeding very heavily."
Police and ambulance crews arrived at the scene and Buster was cornered before he was Tasered and then destroyed by a vet.
The family's three other dogs, two Staffordshire-pit bulls called Axle and Rocky and a Staffordshire called Stitch, were taken to police kennels.
They were undergoing tests yesterday to ascertain whether or not they are dangerous.
Stephen, 45, had split from his wife Teresa, 42, earlier this year. She moved out of the house in Cleator Moor, Cumbria, where Stephen lived with his three kids.
His son Frazer, 19, said: "Dad was a great man, he was like our best mate as well as our dad.
"Nothing was too much trouble for him as far as his kids were concerned.
He loved cooking for us and made great curries and spaghetti bolognese, we're all going to miss him more than we can say.
"He split up with our mum a couple of months ago but she is absolutely devastated."
Inspector Gary Hunter, of Cumbria Police, said: "In 20 years I've never seen anything like that. The dog had been angry for a good three hours or so.
"There was a lot of blood everywhere and the dog was still in a room quite close to the landing.
"The door wasn't that secure and behind the door the dog was barking very loudly and trying to get out."
Buster belonged to Carla, Frazer and Teresa and had been taken in by the family after being abused by a previous owner.
Jade said: "He had never shown any aggression at all in the past, he was a gentle dog and used to like getting into bed with us, we don't know why he suddenly reacted the way he did."
A Cumbria Police spokeswoman said: "The death is being treated as non-suspicious and the Coroner has been informed."http://www.thesun.co.uk/sol/homepage/news/7169251/BREAKING-Man-45-dies-after-being-attacked-by-a-dog-at-his-home.html