Two days after an Elvis impersonator’s online rival pleaded not guilty to sending letters tainted with the ricin toxin to several US officials, the Federal Bureau of Investigation arrested a Texas actress for allegedly sending ricin-tainted letters to President Obama and New York City Mayor Michael Bloomberg in an apparently twisted bid to implicate her estranged husband.

The emergence of ricin, a deadly toxin that can be derived from a common ornamental plant, as a revenge tool is a new twist in the post-9/11 era, in which non-terrorists have ratcheted up their local feuds to national security events by involving high officials like Mr. Obama. A spate of poison-tainted mail escalated terror fears in the wake of 9/11, but these new attacks seem both more bizarre and more mundane, like made-for-tabloid vendettas.

In both cases, police say the people who tipped off authorities ended up being the alleged perpetrators. Earlier this spring, the FBI detained a Mississippi Elvis impersonator, Kevin Curtis, on suspicion he sent ricin-tainted letters to Obama and several other officials.

But this week, a rival, James Everett Dutschke of Tupelo, Miss., was arraigned and pleaded not guilty to charges alleging he sent the letters in order to pin the blame on Mr. Curtis.

It turns out the two men were engaged in a long-running personal feud, much of it carried out on social media, that spilled over into local politics and small town intrigue.

Curtis, the Elvis impersonator, has waged a long-running campaign to expose an apparently imaginary body-part trafficking scheme at a local hospital. His rival, Mr. Dutschke, is a member of Mensa, the high IQ society, a blues band frontman, and failed political aspirant.

"What looked at first like classic terrorism – poisoned letters sent to the president and other public officials – now seems more likely to be the product of a local feud between two not-so-good-old boys straight out of a Faulkner story, albeit with Facebook pages," USA Today reported about the two men in April.

In the case of Shannon Richardson, the actress – who has had roles on shows like “The Walking Dead” zombie extravaganza – allegedly attempted to impart revenge on her estranged husband by sending the letters and then contacting authorities and pointing blame at her husband. Her husband, Nathaniel Richardson, filed for divorce a day before his pregnant wife’s arraignment, after telling authorities she was “intentionally misleading” them. The couple was married in the fall of 2011.

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After the Elvis impersonator incident in which the FBI appeared to have nabbed the wrong guy, the agency took a closer look at Ms. Richardson’s allegations, and a lie detector test apparently showed she was lying. She then admitted to sending the letters herself, the FBI says, but still maintained that her husband forced her to do it.

Richardson is accused of mailing a threatening communication to the president, a felony that could result in 10 years in prison.