A 77-year-old great-grandmother was shot by a lone gunman at the front door of her Monkstown home late on Thursday night while her six-year-old great grandson slept in an upstairs bedroom.

The woman suffered a gunshot wound to her lower leg after which the gunman ran away.

She was treated at the scene at Oliver Plunkett Avenue in south Dublin by gardaí and paramedics before being taken to St Vincent’s hospital with injuries which are not thought to be life threatening. The child was unharmed.

Gardaí described the attack as both “highly unusual” and “very, very, callous” and while they do not believe the woman was targeted directly, they said there was “no doubt the house was the intended target”.

One of the woman’s adult grandsons also lives in the house in the quiet cul de sac just a stone’s throw from the centre of the village and although he was at home at the time of the shooting he was uninjured.

The investigation is being headed up by Superintendent Martin Fitzgerald from the Dun Laoghaire Garda station. He appealed to local people with may have witnessed the shooting to come forward as investigating officers are working with “very little information”.

Supt Martin Fitzgerald of Dun Laoghaire Garda Station briefing media. Photograph: Collins

At a press briefing at the scene Superintendent Fitzgerald said: “Shortly after 11pm last night the lone gun man presented at this house... banging on the door”.

When the woman opened the door he fired at least two shots from a hand gun. “One of those shots injured the 77-year-old female in the lower left leg. After which, the lone gunman made his way out of this cul de sac on foot. We have no further information about which direction he took or how his departure was facilitated,” the superintendent said.

A forensic examination of the scene suggested that the attacker had used a hand gun. Superintendent Fitzgerald said the investigation would “follow all lines of inquiry to detect this very, very, callous attack”.

The attacker, who did not speak, was wearing dark clothing and was said to be between 5 ft 7 and 5ft 10. Nothing else is known about his appearance.

“The house is occupied by the grandmother of the family. Residing here with her are her two grandsons. They are adult grandchildren and one was present at the time. Also in the house was a six-year-old great grandson.”

Local people were shocked by the shooting. One local shop worker described the victim as “ a lovely lady”.

She declined to be identified but said the woman was a regular visitor to her shop and a woman “who would do anything for anyone. It is just so shocking that something like this could happen here.”

Anyone with information is being urged to contact (01) 6665000, (01) 6665032,or the confidential line on 1800666111.