This Australian Commerce Student Just Won Our First Gold Medal In Rio

He beat China's defending champion Sun Yang who he called a "drug cheat".

Mack Horton, 20, won Australia's first gold medal at the Rio Olympics in the men's 400 metre freestyle.

David Mariuz / AFP / Getty Images

Horton, who is enrolled in a commerce degree at the Australian Catholic University, screamed "oi oi oi!" at his Australian team mates as he exited the pool after taking just 3:41.55 seconds to swim 400 metres.

Horton said it was "definitely" a win for "the good guys" as he beat defending champion, China's gold medallist Sun Yang, who tested positive for a doping swab in May 2014.

Quinn Rooney / Getty Images

China's Sun Yang reacts after placing second in the Men's 400m Freestyle Final during the swimming event at the Rio 2016 Olympic Games at the Olympic Aquatics Stadium in Rio de Janeiro on August 6, 2016.

Horton yesterday called defending champion Yang a "drug cheat" and today said there was a rivalry between himself and "athletes who have tested positive".

Christophe Simon / AFP / Getty Images

Australia's Mack Horton reacts after he won the Men's 400m Freestyle Final during the swimming event at the Rio 2016 Olympic Games at the Olympic Aquatics Stadium in Rio de Janeiro on August 6, 2016.

"What just happened?" a disbelieving Mack told the Seven Network.

"I just kept telling myself that I had this that I was in control and that I could do it."