How did Jae Crowder flip this insane shot into the basket?

Jae Crowder's offensive ability is extremely limited. He can make open threes, finish in transition and live off solid cuts away from the ball. But all in all he isn't paid to score.

That's what makes this shot during Sunday's game against the San Antonio Spurs so amazing. 

Well, it would be amazing no matter who pulled it off, but Crowder doing it is especially crazy.