For the past six years, United States postal inspectors have been chasing an individual who mailed hundreds of letters containing white powder to locations around the world.

On July 28, the U.S. Attorney’s office in Dallas announced that a joint FBI-Postal Inspection Service investigation had identified the mailer as Hong Minh Truong, 66, of Roland, Texas. Charged with false information and hoaxes, Truong was arrested and placed in jail.

None of the letters contained poisons or toxins, but more than 500 letters with a white powdery substance were mailed from north Texas, the investigators said.

“Mr. Truong’s alleged criminal activities caused emergency responders and hazardous response teams immense unnecessary labor and expense, diverted personnel from actual emergencies and caused untold emotional distress to those who received the letters,” U.S. Attorney Sarah R. Saldana said in a news release.

According to the investigators, the letters contained warnings and mocked law enforcement for their shortcomings. “You all flaming idiot, ignorant and arrogant, know nothing!” said one. “We claim everything.”

If convicted, Truong could face five years in prison and a $250,000 fine.