A Melbourne gunman who left threatening notes in a letterbox drop telling residents their pets would die has already shot dead three cats.

Residents in Melbourne’s west fear the gunman will continue his cruel killing spree, with police now trying to identify the attacker.

A three-year-old cat was lucky to escape an attack in Altona North, after being shot with a .22 calibre rifle.

The moggy was forced to learn how to walk again after the cruel act.

View photos A cat survived the cruel act. Source: 7News More

View photos An X-ray of the cat's gunshot injuries. Source: 7News More

“He’s got an amazing personality, he’s very trusting despite all that he’s gone through,” vet Dr Nadian Wong said.

“He’s a very brave cat.

“Using guns is not the way to (threaten and kill off pets).

“It creates fear and anger in the community and I hope we don’t see this again.”

View photos The Melbourne street where the cat was shot. Source: 7News More

RSPCA spokesperson Daniel Bode labelled the act as “shocking”.

“These are shocking acts of cruelty,” Mr Bode said. “The use of weapons or firearms or cross bows can cause significant harm.”

View photos The cat is recovering at a Melbourne vet. Source: 7News More

Another cat was shot twice on the same Altona North street and could not be saved. A third was targeted in nearby Point Cook.

Vets are urging pet owners to keep their animals inside as police work to find the killer.

A police spokesperson said the attacker faces up to two years’ jail or a fine of up to $75,000.