The suspect, Jay DeVaughn, of Denver, faces a federal charge of mailing threatening communication, according to an arrest affidavit.

The affidavit says members of the Joint Terrorism Task Force observed DeVaughn place mail items into drop boxes at the drive-through mail drop box at the Wellshire Post Office, 2080 S. Holly St., in Denver on Feb. 22. Four suspicious letter envelopes were found in three mailboxes, the affidavit says.

The letters were addressed to the Argentine Embassy.

The sender was listed on the envelopes as a woman with an address in Parker.

Inside each envelope was a plastic sandwich bag containing a "white powdery substance and a single sheet of paper," according to the arrest affidavit. The paper contained more than 200 black-and-white photos of men and women.

"Por los Desparacidos" was written at the bottom of the paper, the affidavit says. The approximate English translation is, "For those who have disappeared."

On Feb. 8, the Argentine Consulate in Los Angeles received a letter containing white powder. That letter was postmarked Feb. 4 in Denver and had the same return address. It contained a message in broken Spanish that translated to, "What dirty fascists, you killed my brother and now you are going to die," the affidavit says.

A similar letter was received by the Argentine Consulate in New York City on Feb. 16. With the same return address and a Denver postmark, the letter contained a message that translated to, "Dirty Fascists; You are going to die like how you kill my friends, Pigs!" the affidavit says.

Since November, the Denver Joint Terrorism Task Force has been investigating white-powder letters sent to Denver representatives and senators. The letters were mailed from Colorado and were received between September and November.

Those letters listed two men as the senders. When contacted by authorities, both men denied sending white-powder letters and said they, too had been harassed and threatened, the affidavit said. One of the men was married to the woman listed in the return address on the letters mailed Feb. 22.

That woman told investigators she had received two threatening messages from a man identifying himself as a former patient. The man said in the messages that the woman, who is a psychiatrist, had taken him off his medication and told him to go to an emergency room.

"How do you want to die?" the man asked in one message, according to the arrest affidavit.

After 12 white-powder letters were mailed in January from Alabama to the offices of Alabama senators and representatives in Washington, D.C., investigators zeroed in a Web site and contacted the ISP provider for that site, the affidavit says. After locating an IP address and then a physical address in Alabama, investigators learned the address belonged to DeVaughn's mother and stepfather and that he had stayed there for five days in December.

The affidavit says that after an "apparent link" was established between DeVaughn and the Alabama white-powder letters, a search warrant was obtained for his office at the Community College of Aurora.

DeVaughn was the college's director of library services.

DNA linked DeVaughn to one of the threatening letters, and witnesses also identified his voice as that in threatening messages, the affidavit says. In addition, DeVaughn's handwriting appears to match handwriting on letters sent to DeGette and Udall.

Mike Coffman said his office found out the white powder was actually corn starch.

"When a congressional office gets a white powder substance, you don't know what it is, so you don't take any chances," he said. "I'm just so glad they caught him, and I hope that sends a message to other folks that might want to do that."

A Udall spokesperson told TheDenverChannel.com that a letter was delivered to his Denver office in November. A person opened the letter, spotted a zip-close plastic bag with white powder in it and called authorities. Workers were held inside for about an hour to prevent spreading a health risk, if one existed, then they were allowed to leave.

The arrest affidavit does not say what the white powdery substance actually was.

Click here to read the arrest affidavit.