Kulish, 28, was in the running for a medal when he blundered. He finished eighth.
“The button on my jacket came undone and I felt some discomfort, but time passed and I had to make a shot,” Kulish, who is ranked second in the world, told reporters afterward.
Kulish “didn’t notice that I was already aiming for someone else’s target,” he said.
“I am not happy,” he added. “Who shoots into someone else’s target? Only people like me.”
China’s Zhang Changhong won gold.
This article originally appeared on HuffPost and has been updated.