Laura Shorthouse, 29, was out walking their eight-month-old dog, Rocco, along Marsden beach when a bull mastiff ran towards her and her daughter, Layla.
She said: "It feels very surreal. This dog just grabbed our little dog out of nowhere. It just shook and shook.
"It happened within minutes. Rocco was just lying there on the floor. He was helpless. He had no chance."
The dog was taken to the vets, but died from its injuries.
The bull mastiff was not on a lead or wearing a muzzle.
Miss Shorthouse said: "I want owners of dogs to take control. If you have a dog like a bullmastiff you should make sure it has a muzzle.
"It is an animal, and you don't know how they will react to certain situations.
"It could have been my daughter the dog went for. Layla has been left traumatised. She is having trouble sleeping."
The Dangerous Dogs Act 1991, which aims to protect people from injury or from fear of dogs, makes it a criminal offence to allow any dogs to be out of control in a public place.
A Northumbria Police spokesman said: “At 6.45pm on Sunday June 30, a woman reported her dog was attacked by another on Marsden beach and later put down.”
Anyone with information should contact police on 101.
(Sky Tyne and Wear - Jul 5, 2013)
