After goalkeeper Ross Glendinning's long kick forward, centre-forward McMurray controlled Cathair Friel's flick-on before unleashing a quick-fire, unstoppable volley over Linfield stopper Gareth Deane, who was in no man's land.
The 2-1 win saw David Jeffrey’s Sky Blues move into seventh spot while Linfield have now lost three of their last five league outings.
MATCH REPORT: Ballymena United stun Linfield at The Showgrounds