It happened at a house in Killinarden Estate in Tallaght on Saturday just after 4pm.The woman, described by police as being middle-aged, was found fatally injured at the scene.Her daughter, who is in her 20s, has been rushed to hospital.Gardaí arrested a man in his 50s, who was also injured, at the scene and recovered a shotgun. He is currently being treated under guard at St James' Hospital for non-life threatening injuries.He is being detained under Section 30 of the Offences Against the State Act, 1939.A statement from An Garda Síochána said: "The scene is preserved for technical examination and the office of the State Pathologist has been notified."Mick McCaffrey, the Sunday World newspaper's Crime Correspondent, said that a man walked into the house and opened fire on the women."It is believed that the mother was shot in the back of the head and was dead at the scene while the daughter suffered some sort of facial injury - she was possibly shot in the face," he said."She's in Tallaght Hospital. Her condition is described as serious - not critical."Meanwhile, a man in his 40s has been shot dead at a house in Lucan, west Dublin.The gun attack took place in Earlsfort View on Saturday at around 7.30pm.He was taken to Tallaght Hospital where he was pronounced dead.The scene has been preserved and the office of the State Pathologist notified.Gardaí are investigating a link between the shooting and a burnt out car found in Glen Vale, Lucan on Saturday night.