Jamie Lynn Gray shot a new Olympic record to claim gold in the women's 50m rifle three positions competition.
The American's 691.9 points tally beat Ivana Maksimovic of Serbia by 4.4 points while Czech Republic's Adela Sykorova took bronze.
Gray, who came fifth in the 10m air rifle, finished just outside the medals in Beijing in 2008.
But the 28-year-old was always in control after also claiming an Olympic record in qualifying.
Gray scored 592 in qualifying, in which scores counted for the final event, and her overall consistency helped beat Maksimovic into second.
Maksimovic scored the best individual round score of the competition - 10.9 - but could not match Gray's all-round form.
The American's Olympic record bettered that of Chinese defending champion Du Li, who was knocked out after finishing 13th in qualifying.
finished down in 42nd.