Former University of Alabama track star Kirani James won his first gold medal on Tuesday in the 400 meters at the IAAF World Championships in Daegu, South Korea.

James was representing his native country of Grenada. James, 18, posted a personal best time of 44.60 to defeat defending champion LaShawn Merritt for the gold medal.

Following the race, James told reporters, “I’m a bit surprised by the win, but I’m happy to come here, represent my country and run a personal best. This means great things not only for me, but the people in my country and the rest of the 400-meter sprinters. I think we have a chance to make it a very competitive event come next year’s Olympics.”

With 100 meters remaining, James was behind more than a meter but ran down Merritt to win by a stride and three one-hundredths of a second at the finish line. With the win, James became the youngest 400-meter world champion in history by more than two years.

“I just tried to stay as relaxed as possible and finish strong,” James said of coming from behind to win.

During his time at Alabama, James won a pair of NCAA outdoor titles in the 400 meters, was a three-time SEC Champion and the 2011 SEC Indoor and Outdoor Runner of the Year.