A 75-year-old man was seriously injured when he was attacked by a stray Staffordshire Bull Terrier.
David Morgan, from Liverpool, is recovering from surgery after the dog savaged his arm.
The animal had gone on the rampage in Ferndale Road, Wavertree, attacking a small Shih Tzu dog and running wild through people’s gardens.
Merseyside Police said officers were called to a report of a dog dangerously out of control on the street on February 14.
A police spokesman said: “Officers were called at around 11.15pm after a Shih Tzu dog being walked by a woman was attacked by a light-coloured Staffordshire Bull Terrier that had appeared from down an alleyway.”
In her efforts to prise the Staffordshire Bull Terrier off her dog, the woman, who is in her 50s, sustained slight injuries to her hand and arm.
Two neighbours who came to the woman’s rescue were also injured by the dog.
It is understood that the dog then attacked Mr Morgan, who was standing between the animal and an eight-year-old boy.
He was bitten when he got the dog in a headlock as he tried to bring it under control.
Officers were able to seize the Staffordshire Bull Terrier, which was without an owner and not on a lead at the time of the incident.
The Shih Tzu received slight cuts and bruises in the attack and has been taken to a vet for treatment.
Inspector Matt Boyle, from Merseyside Police’s dog unit, said: “This was a particularly nasty incident involving what appears to have been a stray dog.
“Incidents involving stray dogs are very rare in Merseyside and every effort is being made to try to establish if the dog has an owner.”
Anyone with any information about this incident is asked to call Merseyside Police on 0151 709 6010, or Crimestoppers, anonymously, on 0800 555 111.