What you see here is the Dallas Mavericks' Ivan Johnson getting tossed from a summer league game against the Charlotte Hornets for
the crime of looking staring at an official and saying "Really, motherfucker?" after having fallen to the floor.
Johnson appeared to trip or be pushed in the back on the play. After the ball went out of bounds, Johnson simply stared at the official, and that was apparently enough for an ejection. Update: As has been pointed out, Johnson also said "Really, motherfucker?" to the official. I had watched it in a Vine (with sound on) and didn't catch it. I apologize for not hearing the "motherfucker."
Somewhat related: Earlier this week, Johnson said that his way of getting back in the league would be to "fuck anybody that's in front me." Keep fucking anybody in front of you, Ivan, because the NBA would be much more fun with you in it again.