Piotr Sujkowski and his 15-year-old daughter, Olivia, watched helplessly as their beloved dog Elfie was mauled to death by a big black dog at a busy northern suburbs dog beach at the weekend.
Mr Sujkowski, of Ballajura, said he punched the larger dog in the head several times to try make it let go of the 4½-year-old miniature schnauzer, but "it was just like hitting bricks" and it would not let go.
The pair had just come out of the water at the northern end of Hillarys dog beach when the larger dog, which they believe was an American staffy, approached just before 5pm on Sunday.
Mr Sujkowski said the owner of the vicious dog did not say anything to them after the attack, but he did put his dog on a leash.
"We were drying ourselves and Elfie was facing us, wagging her tail and waiting for some action," Mr Sujkowski said. "I didn't even see it coming. It just happened so quickly.
"To see her attacked like that was just so traumatic because you can't do anything about it. She was ripped open with her organs spilling out of her."
Olivia said she was extremely upset to have seen her dog savaged, particularly as Elfie was so scared of bigger dogs. "It was the worst thing ever," Olivia said.
Mr Sujkowski said Elfie died after they arrived at Vetwest Animal Hospital in Whitfords, where the vet told them Elfie had the most horrific injuries she had seen.
He hoped witnesses would come forward to help avoid similar attacks on other pets or children.
The dog's owner was in his late 20s, about 170cm tall and had brown to blond spiked hair. He wore a navy blue singlet and large sunglasses.
Olivia's mother, Magda Sujkowski, said they thought of Elfie as part of the family and never did anything without her. "She had so much character," Mrs Sujkowski said. "She was just there doing what she loved most on the beach."
City of Joondalup chief executive Garry Hunt said the council had received a report of a dog attack and was investigating.