A gangland figure serving a life sentence for the murder of Séamus O’ Byrne in 2009 has died in prison.
Eugene Cullen was discovered unresponsive at the Midlands prison in Portlaoise on Wednesday when officers came to unlock his cell.
Prison sources say he is suspected to have died from a heart attack and that incident is not being treated as suspicious.
Cullen was serving a jail term for the murder of father-of-two Séamus O’Byrne (27) who was shot dead by a hooded gunman outside his home in Tallaght in front of his girlfriend and child in 2009.
Mr O'Byrne's girlfriend, Sharon Rattigan, was shot in the leg during this attack.
The Irish Prison Service is investigating the death and there will also be a Garda investigation and a postmortem.