DALLAS—A Rowlett, Texas, man, who admitted mailing hundreds of white-powder hoax letters, was sentenced this afternoon in federal court in Dallas, announced U.S. Attorney John Parker of the Northern District of Texas.

Departing upward from the U.S. Sentencing Guidelines, U.S. District Judge Sidney A. Fitzwater sentenced Hong Minh Truong, 67, to serve a total of 60 months in federal prison. Truong pleaded guilty in July 2015 to an indictment charging five counts of false information and hoaxes. He has been in custody since July 28, 2014.

At the sentencing hearing, Judge Fitzwater noted that Truong’s conduct was significant and dangerous and involved more than 400 threatening letters in multiple batches over more than a five-year period. Truong’s conduct cost emergency and investigative responders more than $2.8 million, which does not include economic losses to businesses, schools and government offices.

According to the factual resume filed in the case, since December 2008, Truong mailed more than 400 hoax letters from the North Texas area to cities across the U.S. and to U.S. Embassies abroad. The initial letters, sent out on December 4, 2008, had a “Dallas, Texas” postmark and contained a white-powder substance. More than 15 batches of hoax letters were sent from the Dallas area from December 2008 to the present. In all but two batches of letters, a white-powder substance was included in the envelope.

The substance contained in the more than 400 letters in this case did not contain Anthrax; however, substantial governmental resources were expended in the response and investigation. Although each response was unique, every response involved multiple agencies dispatching personnel and equipment.

Truong mailed some of the hoax letters to more than 100 elementary schools and daycare centers, including the Mi Escuelita Preschool Crossover, in Dallas; Lockheed Martin Aeronautics in Fort Worth, Texas; the Empire State Building, in New York City; Fenway High School in Boston, Massachusetts; and the Dallas Morning News in Plano, Texas.

The U.S. Postal Inspection Service and the FBI investigated. Assistant U.S. Attorney Errin Martin prosecuted.