Boston Celtics guard Marcus Smart was fined $25,000 after flipping off a fan during the fourth quarter of Tuesday night's Game 2 loss to the Bulls, the league announced on Wednesday. 

Smart, who spent two years at Oklahoma State from 2012-14, clearly let his frustrations boil over with his top-seeded Celtics now facing a 2-0 deficit to the eighth-seeded Chicago Bulls. With six minutes left in the game and his team down 14 points, Smart missed a 3-pointer from the right wing, and as he ran back on defense, Smart directed the obscene gesture at a fan near the court. 

This isn't the first time Smart has had a negative encounter with someone in the crowd. During his sophomore year at OSU, Smart shoved a Texas Tech fan in the final seconds of a loss to the Red Raiders after he claimed the fan directed a racial slur at him.