At 11:00 p. m., the defendant, who was armed as well as masked, accosted a husband and wife in the entrance to their apartment building. The defendant ordered the couple to take him into their apartment. After they entered the apartment, the defendant forced the wife to bind and gag her husband and then to open a safe, which contained a diamond necklace. The defendant then tied her up and fled with the necklace. He was apprehended by apartment building security guards. Before the guards could return to the apartment, but after the defendant was arrested, the husband, straining to free himself, suffered a massive heart attack and died. The defendant is guilty of: