His death is recorded in the Communicants Roll Book of Macosquin Presbyterian Church in 1878, after which, the lady below him, who I am assuming was his wife, Nancy Jane Gray, "removed to Maghera". I have rechecked Civil Records and his death is definitely NOT there.
Civil Deaths shows a Samuel Gray, died 1877, aged 55 - could this be him? It is. Death notice in the Coleraine Chronicle gives his death as 9th December 1877, "at Camus near Coleraine, aged 55".