Abducted from his car, interrogated and shot by the Official IRA. His hooded body was found near the Donegal Border. First UDR officer to be killed. An OIRA statement said, It was established through interrogation, that he was actually working for British Intelligence.

Marcus had previous service with the Irish Guards, was High Sheriff of Co Limavady and Chairman of the Limavady Ulster Unionist branch. 10th UDR member to be killed and 1st officer.