Golfer Segundo Oliva Pinto was neck-and-neck with his opponent going into the final hole in the Round of 16 at the U.S. Amateur on Thursday when a grave mistake by his caddie would end up costing him the entire match.

After Oliva Pinto hit the ball into a bunker in the final hole at Bandon Dunes in Oregon, his caddie Brant Brewer stepped into the sand to test the texture. What looked to be an innocent move was actually a violation of the U.S. Golf Association's rulebook.

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“Before making a stroke at your ball in a bunker, you must not: Deliberately touch sand in the bunker with your hand, a club or rake or any other object to test the condition of the sand and learn information for your next stroke,” Rule 12.2 states.

According to ESPN, Brewer denied touching the sand but video revealed that he had in fact jumped in the bunker and reached down to brush the sand several times.

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“He didn't say anything,” a stunned Oliva Pinto told The Golf Channel of his caddie. “But at this point it doesn't really matter. What happened, happened. He can say anything, but it won't change what happened."

According to the rules, players are responsible for the actions of their caddie and, in this instance, it cost Oliva Pinto the hole and the match.

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Tyler Strafaci, the man on the receiving end of Brewer’s mishap, will go on to the quarterfinals where he will take on Stewart Hagestad.