Gardaí have renewed an appeal for information on the 2008 murder of Andrew Burns.
The 27-year-old was shot dead at Donnyloop, Castlefin, Co Donegal, by dissident republicans.
Tomorrow marks 15 years since his death.
The shooting happened shortly after 7pm on 12 February 2008.
Mr Burns was later found on a road close to Donnyloop Church and pronounced dead shortly before 8pm.
Gardaí believe a number of individuals were involved in his murder.
Martin Kelly, from Strabane in Co Tyrone, was sentenced to life in prison for the murder in 2012.
Mr Burns was involved with the dissident republican group Óglaigh na hÉireann, as was Kelly.
In a statement, gardaí said Mr Burns’ family remain "devastated by this heinous act and continue to struggle to come to terms with his murder".
"An Garda Síochána are very grateful for all the witnesses that have come forward and made statements in the intervening years," it said.
"As we approach this 15th anniversary, An Garda Síochána is urging anyone with any information, no matter how insignificant it may seem to them, to come forward and speak with An Garda Síochána.
"In particular the investigation team at Letterkenny Garda Station would like to specifically appeal to the occupant or occupants of a red vehicle that it is believed to have been in the car park at Donnyloop church at around 7pm on the evening of Andrew's murder.
"The investigation team do not believe that the occupant or occupants of this red vehicle were in any way connected with the murder of Andrew but they may have vital information to offer due to their presence at the carpark at Donnyloop church on the evening in question."
Anyone with information is asked to contact Letterkenny Garda Station on 074 9167100, the Garda Confidential Line 1800 666 111 or make contact with any garda station.
