Watch: Marcus Smart flips off fan sitting courtside

You know things are looking bleak when you're flipping the bird to fans in your own building.

After missing a 3-pointer Tuesday with his Boston Celtics down 14 to the Chicago Bulls late in the fourth quarter, guard Marcus Smart gave the middle finger to a fan sitting courtside who clearly said something that rubbed him the wrong way.

Smart finished with 13 points on 6-of-11 shooting, eight rebounds, two assists, two steals, two blocked shots, and one obscene gesture in 27 minutes off the bench as Boston fell 111-97 at the TD Garden.