Ginny Thrasher reacts after winning the 10m air rifle final Saturday on the first day of competion at the Rio de Janeiro games. (Valdrin Xhemaj/EPA)

Ginny Thrasher is the cheery owner of a menacing name, a soft smile and a high-powered, German-made weapon that easily could be a mistaken for a prop from a science fiction movie.

“It looks like a gun from outer space,” Thrasher conceded.

The 19-year-old Springfield native is also now the proud owner of an Olympic gold medal, the surprising winner of the women’s 10-meter air rifle competition Saturday morning. The win marked the first medal awarded at these Rio Games and also the first big upset.

Four years ago, Thrasher was still new to shooting. She began hitting the range the same month as the London Olympics.

“I remember watching the Games,” she said, “and watching the men’s air rifle event and not even knowing the rules or how it works. I’m very thankful to be able to be here four years later.”

She wasn’t merely “here” in Rio, where the best athletes on the planet have converged in this embattled corner of paradise. She was among the biggest U.S. stars of the opening day of the Summer Games. Thrasher set an Olympic record with her score of 208.0 in the final, topping two Chinese shooters — Du Li and Yi Siling — who have won six Olympic medals between them.

“This is beyond my wildest dreams,” said Thrasher, who’s just a couple of months removed from her freshman year at West Virginia.

She grew up fantasizing about making the Olympics but not as a shooter. The idea of yielding a gun and taking dead aim at a target nearly 33 feet away was completely foreign. Thrasher wanted to be a figure skater, something she competed in through high school, dancing and twirling to music.

“It was something I loved, but it was a hobby,” she said. “I kind of dreamed of going to the Olympics in it, but it was a very unrealistic dream.”

Thrasher didn’t fire her first gun until barely four years ago after begging her grandfather to take her hunting. She went through gun-safety training, learned to shoot from her father, who’s retired from the Air Force, and when Thrasher bagged her first white-tailed deer, she was hooked.

She later joined the air rifle team at West Springfield High — her daily routine: figure skating lessons in the morning, then classes and shooting practice after school — before enrolling last year at West Virginia, a shooting powerhouse that has won the past four NCAA championships. As a freshman last season, Thrasher won both the individual small-bore and air rifle titles, vaulting her onto the Olympic radar.

She came to Rio as the youngest member of the 15-member U.S. shooting team, ranked No. 23 in the world and wasn’t considered a serious medal threat by most, not with so many experienced shooters in the field. Du, a four-time Olympian, took gold in the 10-meter event in 2004 when Thrasher was all of 7 years old. And Yi won the competition at the London Games when Thrasher was barely a freshman in high school, not yet old enough to drive.

Despite her lack of experience, Thrasher woke up with confidence Saturday morning and was eager to take her black Feinwerkbau 700 air rifle to the range. Staring down the target, she posted just the sixth-best score in the morning qualifying round but benefited from a key rule change at these Rio Games: For the first time at an Olympics, scores zero out after qualifying and shooters enter the finals with a clean slate.

The pressure was heavy, and the stakes high. A racing heart and labored breathing has doomed more seasoned competitors. But Thrasher kept her sights on the target, not the podium.

“In those moments, you really have to focus on what’s important. The medals are amazing. But it’s not what’s important,” she said. “What’s important is taking the best shot you can and giving your all. . . . The medal is just an outcome of what I’m doing.”

When the eight best shooters returned to the competition field for the finals, no one stood a chance. Thrasher opened the finals with a bull’s-eye that yielded a perfect score of 10.9, setting a high bar for the rest of the field. And for herself.

“To come away with a 10.9 on the first shot, obviously create a lot of confidence,” she said. “It says a statement: ‘Ginny’s here to win.’ ”

Thrasher cruised through her remaining shots, topping Du by a full point and winning by a final tally of 208-207.

Thrasher has a shot at one more medal here later this week, competing in the 50-meter rifle three positions event Thursday. And then she’ll board a flight home — a new gold medal included with her carry-on luggage — to begin her sophomore year at West Virginia, where she’s an engineering major.

“I get home 20 hours before the first class,” Thrasher said. “So I’ll be in physics at 8:30 a.m.”

She has three years remaining in her college career, and she hopes at least a couple of more Olympic appearances ahead of her. No doubt she won’t be entering future competitions as an underdog.

“For me, having that less expectation maybe has helped me,” she said, “but now I’m ready to handle that expectation and to go forward with my career.”