Clifford Clarke, 79, was in the garden of his home in Clubmoor, Liverpool, when the dog attacked around 8.30pm last night, Merseyside Police said.
A force spokesman said a post-mortem examination this afternoon had revealed Mr Clarke died from “multiple injuries consistent with a dog attack”.
“His next of kin and a family member have both now been informed of his death and family liaison officers have been appointed to provide support and updates regarding the police investigation,” he said.
Two local women aged 27 and 28, arrested last night on suspicion of an offence under the Dangerous Dogs Act, 1991, were arrested again under the more serious charge today.
They remain in custody and were still being interviewed by detectives on Sunday evening.
Armed unit
Merseyside Police said earlier that officers had found Mr Clarke lying on the ground with the dog nearby and had called in an armed unit to shoot the animal.
“When they arrived, officers found the body of the man and they were confronted by a dog that was out of control,” a police spokeswoman said.
“Armed officers attended at the scene and the dog was destroyed. At this stage the breed of the dog is still to be established.”
In March a 14-year-old girl died after she was attacked by a pack of dogs at a house in Greater Manchester.
Jade Anderson was savaged by up to five dogs at a house she was visiting in Chaucer Grove, Atherton near Wigan.