UTICA, N.Y. (AP) — An upstate New York man has pleaded guilty to charges he mailed 21 death threats with white powder over 15 years to U.S. Sen. John McCain, a local high school and others.

Federal prosecutors say Brian Daniel Norton pleaded guilty Friday to two federal counts of conveying false information and hoaxes. He faces up to 10 years in prison at his April 10 sentencing.

Prosecutors say that between 1997 and 2012 the 59-year-old Norton mailed letters with white powder he claimed was anthrax or ricin. The powder was harmless.

His targets also included former Secretary of Defense Robert Gates and former U.S. Rep. Ann Marie Buerkle of New York.

Norton also sent threatening letters to a high school and college in Syracuse.

Norton's federal defender didn't immediately return a message.