"A furtive movement in such cases is a movement reasonably consistent with going for a weapon and not reasonably consistent with anything else under the circumstances.
"The law does not demand that your perceived antagonist have a real weapon in order for you to employ lethal force in self defense. It only demands that his actions create in your mind a reasonable and prudent belief that he has a weapon. If he is close enough to employ such a weapon, and if his actions are consistent with an armed person trying to kill you (Diallo turned suddenly and thrust the hand with the black object toward the officers), then the requirements have been met for you to justifiably use deadly force in order to defend your own life."
"Skulking in the Vestibule" by Massad Ayoob