After committing a rash challenge which he was booked for he picked up the ball, walked away with it, then shoved it into Gayle's stomach. Nor the referee or the linesman saw it, but the 4th official did. He could easily have been sent off for that alone as the force he did with could be classed as assault.
This. Should have been a red on its own for violent conduct, credit to the 4th official for getting involved though