NightSide - Good Samaritan or Overzealous Vigilante?

BOSTON (CBS) - In a surveillance video now going viral on social media (which you can watch on the NightSide Facebook page by clicking here) a young man with a gun and a knife attempts to rob a Starbucks. While he is engaged in conversation with the cashier, a bystander picks up a chair and attacks the would-be robber. In the ensuing struggle, the bystander is stabbed in the neck, but manages to wrestle the knife away from the culprit, and ends up stabbing him 17 times. Now, the parents of the robber are threatening to sue the Good Samaritan, claiming that he used excessive force. Do you agree, or did the robber get what he had coming to him?