Here is the video of Paul Pierce flashing gang signs during an NBA playoff game. The Boston Celtics star was fined $25,000 by the NBA for this display. The gang signs occur at the 30 second mark on the tape, and reviewed again at the end.
The incident occurred late in the 4th quarter of the conference finals against the Atlanta Hawks after the opponents had put the game away.
The Paul Pierce gang sign incident is causing the NFL to take a look at possible activity in their league. The NFL has hired experts to study films of on-field celebrations after sacks and touchdowns, something the referees and league officials suspect is occurring on the field.
The sign Paul Pierce flashed was a letter B, an unmistakable emblem of the Piru Bloods. He flashed it at Hawks player Al Horford. In less obvious cases, it will be difficult to discern a threatening sign with something meant to be fun or entirely innocent.