After nearly six years and more than 500 letters, the FBI believes it has found the source of an elaborate white-powder hoax, and it leads directly to North Texas. Hong Minh Truong, a 66-year-old Rowlett man, was arrested July 28 on federal charges of false information and hoaxes.

The U.S. Attorney's Office and the FBI released a joint statement on the investigation, which dates back to December 2008 and spans locations across the globe. The presence of a mysterious white powder on letters prompted rigorous screening and coordination of local, state and federal law enforcement. In all cases, the powder was found to be harmless.

According to court documents, 28 public schools in Boston received threatening letters in June 2013. Other locations that were targeted include Lockheed Martin in Grand Prairie; New Jersey hotels near MetLife Stadium, the site of the 2014 Super Bowl; and U.S. Embassies in Berlin, Paris and Rome.

"The language used in the letters as well as the method of sending the letters, indicate that one person, Truong, is responsible for sending all of the hoax letters," the statement reads.

The letters, which were mailed from Dallas and surrounding cities, contained nonsensical references to Scooby Doo, Al Qaeda, "bad cops" and other law enforcement agencies.

"Where are you Scooby Doo, Counter Intelligence, CIA, you do not know how to catch the triple dealer spy in your law enforcement," an excerpt from the letter reads. "What the hell where are you Scooby Doo, Internal Affairs, FBI, you don't know how to arrest the bad cop in your law enforcement."

The FBI was able to trace the origin of the letters to an IP address in Rowlett belonging to Truong. There's scant evidence of a motive for his actions, though court documents reference a 2002 claim by Truong that he believed the FBI was "beaming radar into his body."

"Mr. Truong's alleged criminal actions 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 Saldaña said.

This is the second bizarre letter-mailing crime linked to Texas recently. On July 16, Texas actress Shannon Guess Richardson was sentenced to 18 years in federal prison for sending ricin-laced letters to President Barack Obama and other officials.

Truong is being held without bond until an August 4 hearing. If convicted, he faces up to five years in prison and a $250,000 fine.