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Army Sgt. Bowe Bergdahl left a letter the night he disappeared from his base in Afghanistan saying he wanted to renounce his citizenship, according to sources, and previously expressed his disillusionment with the Army, telling his father in an e-mail he was "ashamed" to be an American.

That account, though, is being called into question amid conflicting claims over whether Bergdahl left a note behind. U.S Army officials who have read the investigation document said there was no reference in that report to a letter.

While Bergdahl remained at a U.S. military hospital in Germany following a swap for five high-level Taliban members — dubbed a jihadist "Dream Team" — two of Bergdahl’s fellow soldiers told Fox News Channel that the 28-year-old Idaho native willingly walked away from his post in Afghanistan on June 30, 2009. Their claims that Bergdahl's departure from the base was premeditated jibes with emails published in 2012, in which he told his father of his growing disenchantment with the Army's mission in Afghanistan.  [audio-clip]

“The future is too good to waste on lies,” Bergdahl wrote his parents. “And life is way too short to care for the damnation of others, as well as to spend helping fools with their ideas that are wrong. I have seen their ideas and I am ashamed to even be American. The horror of the self-righteous arrogance that they thrive in. It is all revolting.”

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    Bergdahl's father, Bob Bergdahl, who learned the Pashto language spoken in much of Afghanistan while his son was held hostage and chanted an Islamic prayer as he stood alongside President Obama for Saturday's Rose Garden announcement of the deal, wrote back to his son with a subject line in all capital letters: "OBEY YOUR CONSCIENCE!" That email, one of several between the Bergdahls revealed in a lengthy 2012 Rolling Stone report, was sent three days before the-then private first class left his post.

    Fellow soldiers who remembered Bergdahl as an outsider who studied Rosetta Stone lessons in the native language and talked of hiking to China, told Fox News they believe Bergdahl is a deserter, an offense punishable by death in the military code of justice.

    “Yes, I do believe he deserted, without a doubt in my mind,” Cody Full told Megyn Kelly Monday. “He did not serve the United States with honor. We all took an oath — he violated his oath when he deserted us and put other Americans in jeopardy.”

    Despite the conflicting claims, sources who had debriefed two former members of Bergdahl’s unit told Fox News Bergdahl left behind a note the night he left base in which he expressed disillusionment with the Army and being an American and suggested that he wanted to renounce his American citizenship and go find the Taliban. U.S. military officials would not confirm the existence of the letter, but if it does exist, it would likely be part of the original file on the investigation into Bergdahl’s disappearance.

    Some of Bergdahl’s activities prior to his disappearance, including reportedly mailing his gear home, indicated premeditation, according to Full, a 25-year-old former infantryman now living in Houston. It bothers them that a soldier they believe betrayed his comrades, possibly leading to their deaths in subsequent rescue efforts, could be seen as a hero.

    “I just don’t want to see him hailed as a hero and I just want him to face the consequences of his own actions and possibly face court-martial for desertion,” Gerald Sutton, a 31-year-old Michigan college student who left the military in 2012 after serving with Bergdahl in Afghanistan, told Kelly.

    The accusations are not new. Almost from the beginning, there were questions about the circumstances that led to Bergdahl's capture. He would later say on a hostage video released by his captors that he had been snatched after falling behind his patrol. But a Pentagon probe in 2010 concluded that evidence was “incontrovertible” that Bergahl walked away from his unit near the Pakistan border, according to a former Pentagon official who has read it. The military investigation was broader than a criminal inquiry and didn’t formally accuse Bergdahl of desertion, though with his return, it is unclear what, if any, punishment he could face.

    Members of his unit, during interviews as part of the probe, characterized Bergdahl as a naïve, “delusional” soldier who thought he could help the Afghan people by leaving his Army post, according to the official who spoke on condition of anonymity. But fellow soldiers were sworn to secrecy, according to Nathan Bradley Bethea, who served in the same 1st Battalion, 501st Parachute Infantry Regiment as Bergdahl and took part in efforts to find him. Writing for The Daily Beast, Bethea said he felt he could come clean about Bergdahl without violating those orders.

    "After we redeployed, every member of my brigade combat team received an order that we were not allowed to discuss what happened to Bergdahl for fear of endangering him," Bethea wrote. "He is safe, and now it is time to speak the truth.

    "And that the truth is: Bergdahl was a deserter, and soldiers from his own unit died trying to track him down."

    The parents of one soldier who died in Afghanistan in 2009 – allegedly during the search for Bergdahl -- told Fox News on Tuesday that their son, 2nd Lt. Darryn Andrews, regarded Bergdahl as a deserter.

    “I think he should be tried as a deserter,” said his father, Andy Andrews. He and wife Sondra Andrews said they learned from posts on Facebook that their son was apparently involved in the hunt for Bergdahl when he was killed in an ambush.

    During his captivity, military officials decided against making an extraordinary effort to rescue Bergdahl after weeks of intensive searches, particularly after it became evident he was being held in Pakistan under the supervision of the Haqqani network, an ally of the Taliban with links to Pakistani’s intelligence service. Yet Bergdahl was promoted twice while in captivity, most recently to sergeant, in 2011. He was slated to be promoted again this month to staff sergeant, but a U.S. military spokesman told Fox News that is on hold now that he is out of captivity.

    Pentagon officials have maintained the circumstances of Bergdahl’s capture were irrelevant, and President Obama on Tuesday defended the decision, saying his administration had consulted with Congress about the possibility "for some time."

    "Regardless of the circumstances, whatever those circumstances may turn out to be, we still get an American soldier back if he's held in captivity," Obama said during a news conference in Poland. "We don't condition that."

    Earlier, National Security Advisor Susan Rice said on Sunday that Bergdahl "served with honor and distinction."

    Republicans in Congress, meanwhile, have criticized the swap and complained of not being consulted, citing a law that requires Congress to be given 30 days' notice before a prisoner is released from Guantanamo Bay. Republicans on the House Armed Services Committee said the Pentagon notified the panel by phone on Saturday that the exchange was occurring in the next five hours.

    U.S. and Taliban officials hammered out the deal indirectly, with the government of Qatar serving as an intermediary. The U.S. and Qatar then signed a memorandum of understanding governing the conditions of their release. Beyond the travel ban, however, the exact stipulations are unknown.

    Obama on Tuesday also acknowledged there’s always a chance that the released prisoners could rejoin the Taliban or other terror networks intent on harming Americans. If they take those steps, Obama said the U.S. "will be in a position" to go after them.

    The Taliban demanded the release of these specific commanders, the former Pentagon official said, and the U.S. initially wanted to free them in batches to ensure that Qatar could hold up its end of the bargain. Days before the deal was announced, Bob Bergdahl sent out a bizarre tweet that has since been deleted without explanation:

    "I am still working to free all Guantanamo prisoners. God will repay for the death of every Afghan child, ameen."

    In Bergdahl's hometown of Hailey, Idaho, yellow ribbons adorn signs and trees along the main drag. Mayor Fritz Haemmerle said the city plans a June 28 welcome home celebration for Bowe, but added that, "If objective facts and a careful consideration reveal that Bowe Bergdahl should face consequences in a United States courtroom, then the United States should do what it believes it necessary.”

    As the military decides what to do with Bergdahl, his own words in the emails reported by Rolling Stone's Michael Hastings, who died in a mysterious car accident last year, could come back to haunt him.

    “In the U.S. Army you are cut down for being honest … but if you are a conceited brown-nosing sh-- bag you will be allowed to do whatever you want, and you will be handed your higher rank … The system is wrong,” Bergdahl wrote. “I am ashamed to be an American. And the title of U.S. soldier is just the life of fools.”

    Fox News Channel's Jennifer Griffin and The Associated Press contributed to this report.