The FBI is questioning a person of interest who may be involved in sending letters laced with the poison ricin to NewYork Mayor Michael Bloomberg and President Obama.

ABC News:

The agents are questioning a man from New Boston, Texas, whose wife called authorities after she noticed strange material in her refrigerator, and noticed computer searches for ricin, the source said.

The source called the development a promising lead in the case.

Images obtained exclusively by ABC News of one of the threatening letters sent to New York Mayor Michael Bloomberg show the substance authorities suspect is ricin.

The images show globs of a pinkish, tan substance splattered on a typed letter bearing an anti-gun control message. A similar letter was sent to President Obama at the White House and a Bloomberg-connected office in Washington D.C., police said.

"You will have to kill me and my family before you get my guns," the letter reads. "Anyone wants to come to my house will be shot in the face. The right to bear arms is my constitutional God-given right and I will exercise that right 'til the day I die. What's in this letter is nothing compared to what I've got planned for you."

The letters never made it to Obama or Bloomberg and today the U.S. Postal Service said none of the letters posed a health risk. The letters -- all reportedly with identical text -- are postmarked May 20 from Shreveport, La.

The FBI says that whoever sent the letters didn't know what they were doing and risked poisoning themselves rather than the targets. Clearly, whoever wrote the letters is a very disturbed person and the sooner they are taken into custody the easier we all can breathe.