NEW YORK (AP) — A powdery substance was found Friday with a threatening letter in a mailroom at the offices of Manhattan District Attorney Alvin Bragg. It’s the latest security scare as the prosecutor weighs a potential historic indictment of former President Donald Trump. The letter said, “Alvin, I am going to kill you,” according to a person familiar with the matter. The person was not authorized to speak publicly about an ongoing investigation and did so on condition of anonymity. The discovery, in the same court building where a grand jury is expected to resume work Monday on the Trump case, came amid increasingly hostile rhetoric from the Republican.