TUPELO, Miss. -- Federal agents of all sorts invaded northeast Mississippi several days ago on a mission: Find the man who sent a poison-laced letter to the president. But the United States government quickly found itself entangled, once again, in a misunderstood land dominated by squabbling tribes and petty vengeances.After two arrests, investigators concluded that what they had descended upon was probably less about the president -- or the U.S. senator and retired judge who also received letters -- than a serious case of indigenous bickering.That shocks no one here. "Tupelo is a kaleidoscope," said sociologist Mark Franks, who grew up in nearby Booneville. There are true geniuses walking the streets of Tupelo, he said, and incredibly wealthy, generous people. But also, "every wall-eyed uncle and 'yard cousin' -- just referencing the local pejorative -- makes it into Tupelo, Miss. It creates a peculiar culture."Looking for the sender of ricin-laced letters to President Barack Obama, Sen. Roger Wicker, R-Miss., and retired Mississippi Judge Sadie Holland, agents from the FBI, Secret Service and other agencies quickly nabbed Paul Kevin Curtis of nearby Corinth. But the FBI released him Tuesday for lack of evidence. Within hours agents had raided the home of his archenemy, J. Everett Dutschke, karate instructor.Curtis, 45, and Dutschke, 41, have interacted for years, feuding over small-town grievances as labyrinthine and intricate as any global conspiracy. They met in 2005 and were friendly for a time. When he wasn't teaching karate, Dutschke worked for Curtis' brother Jack at an insurance office. Both men knew Wicker, and both had connections to the 80-year-old Holland.It's unclear when hostilities began, but a few years ago Curtis, who worked at the local hospital, developed a theory that doctors were harvesting organs to sell on the black market. He wrote a book about it. Dutschke published a local newsletter at the time and after some negotiations apparently rejected Curtis' writings.Both men have made multiple trips to jail. Curtis was arrested on suspicion of, among other things, assaulting a Tupelo lawyer -- for which he received a six-month sentence from Holland. In January, Tupelo authorities charged Dutschke with molesting children. He pleaded not guilty, but he shut down his karate school while awaiting trial.