Smart tried to block Jaye Crockett's dunk attempt from behind with 6.2 seconds to go and tumbled into the front row of the crowd. He was helped to his feet by one man but then got in the face of another fan in a black shirt.
The man appeared to say something to Smart, who then shoved him with two hands. The fan stumbled backward a bit but didn't fall.
Teammates quickly pulled an angry Smart away from the fracas, and he pointed back in the direction of the fan. Smart was called for a technical foul but was not ejected.
Crockett scored 21 points and tied his season high with 12 rebounds to lead Texas Tech, which handed the Cowboys (16-7, 4-6 Big 12) their fourth straight loss.
The game was tied at 61 when Crockett hit the go-ahead shot with 41 seconds remaining. Oklahoma State's Le'Bryan Nash lost the ball in the lane, and Crockett raced toward the basket at the other end.
Smart knocked the ball away and was called for a foul, then pushed the fan and drew the technical. Dusty Hannahs and Crockett each made one of two free throws for the final margin.
The Red Raiders (12-11, 4-6) earned their second win over a Top 25 team in the past month. They beat then-No. 12 Baylor in January.
The game was tied 13 times and the lead changed 12 times as each team put together runs throughout the game.
Texas Tech dominated inside, getting 32 points in the paint to 22 for the Cowboys.
Smart scored 22 points and Phil Forte had 15 to lead the Cowboys.
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