In a Factor exclusive last night, Bill O'Reilly spoke to former U.S. Marine Jon Hammar, who was held in a rundown Mexican prison for more than four months on a gun charge.

Hammar, 27, was arrested at the border when he tried to enter Mexico with an antique shotgun and was chained to his bed at times during his incarceration.

He explained that he and his friend were told by U.S. officials in Texas that they could cross into Mexico with the gun as long as they filled out a form and brought it with them. But the information turned out to be inaccurate because they were taken into custody. His friend was released after a few days in jail, while he was taken to a prison in Matamoros.

Hammar said there were immediate threats

against him and extortion attempts when he entered the prison. He was eventually moved to a single cell away from the general population.

"They call your family, they throw threats at you and your family, and tell you that 'we need your money.' ... There was threats on my life when I initially got in there," he said, explaining that "they roughed me up a little bit."

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  • "I think I did all right, because I'm alive right now," he said, though his health deteriorated significantly toward the end of his incarceration due to a lack of adequate food and water.

    He said to pass the time he read a book about the Korean War and almost the entire Bible. Hammar said he had no idea until "late in the game" that The O'Reilly Factor and other media outlets were publicizing his plight, and trying to get him out of prison.

    After the terrible ordeal though, he said he doesn't feel any lingering bitterness toward Mexico.

    "I think Mexico is a great place. I really wish, like everywhere, it could kind of get its act together," said Hammar, who thanked O'Reilly, Rep. Ileana Ros-Lehtinen (R-Fla.) and Sen. Bill Nelson (D-Fla.) for their efforts to secure his release.

    Watch the interview:

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