Shay O'Byrne was shot dead in a gun attack in Tallaght

Shay O'Byrne was shot dead in a gun attack in Tallaght. His girlfriend suffered a gunshot wound to the leg. His murder is being linked to an ongoing bloody feud between some of Dublin's major criminal gangs based in the Crumlin and Drimnagh areas.Four people arrested over the gangland killing of a leading Dublin criminal have been released.The four - a 16-year-old girl and three men - were detained at Terenure, Tallaght and Rathfarnham garda stations. Gardai said they have been released and files are being prepared for the Director of Public Prosecutions.