A Pennsylvania man was charged with threatening to kill President Joe Biden and the U.S. representative at the head of the committee investigating the Jan. 6 Capitol riot, prosecutors said.

Robert Maverick Vargo, a 25-year-old from Berwick, Pennsylvania, is alleged to have mailed a threatening letter and a white powder to the office of Rep. Bennie Thompson (D-MS), who is also the chairman of the Jan. 6 committee.

“I’m going to kill you!” the letter said in part, according to prosecutors. “I will make you feel the rest of our pain & suffering. … I am going to kill you & those you love. … You & Joe Biden soon will face death for the wrongs you’ve done.”

Prosecutors stated that Vargo’s letter alluded to “anthrax,” a white powder used as a biological weapon, and “specifically referenced” Thompson’s role leading the Jan. 6 committee.