Gajic, 27, rocketed the ball into the corner of the net past his own goal keeper in the Swiss Super League game on Saturday against Saint Gallen.
The Serb was evidently trying to clear the ball but a video of the kick looks like he was intentionally shooting for an own goal.
His unintentional shot is being described as the greatest own goal ever scored in football history.
His half-volley from well outside the penalty area put Saint Gallen ahead 2-1.
Young Boys came back with a goal to salvage a draw.
By late Monday more than 700,000 people had clicked on the YouTube video that captures Gajic's foulup for posterity.
Was this the worst (or best) own goal ever?
Take a look for yourself: