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(CNN) -- Just weeks before U.S. Army Sgt. Bowe Bergdahl walked off base and into Taliban hands, a British filmmaker caught on video scenes that would come to define his unit as an unruly, undisciplined bunch.
The video, published by the British newspaper The Guardian, showed some soldiers breaking Army rules by not wearing helmets while in the field. Filmmaker Sean Smith filmed Bergdahl and his platoon in 2009 as they built a fortified bunker near several villages in the Paktika province of Afghanistan.
One of Bergdahl's fellow soldiers can be heard sympathizing with Afghan villagers in the video.
"They (Afghans) got (messed) with from the Russians for 17 years, and then now we're here. I'd gladly leave them alone," the soldier says.
An Army source tells CNN discipline in the platoon was "lax." A sergeant was demoted and two other sergeants were re-assigned after the pictures became public, according to a 2012 Rolling Stone article.
Bergdahl's former team leader, Sgt. Evan Buetow, said the footage was blown out of proportion.
"There were some people who were really angry that soldiers weren't wearing their protective equipment out in the field. It was something that got exaggerated way bigger than it should have," Buetow told CNN, adding that soldiers were disciplined.
A U.S. official who has been briefed on the initial Army fact-finding investigation conducted in the months after Bergdahl disappeared told CNN that some of Bergdahl's teammates said he had expressed "boredom" and thought his unit was too passive and should have been "kicking down doors," the official said.
A former lieutenant colonel who advised officials investigating Bergdahl's disappearance said that while some of the unit's commanders did not have their act together, their behavior does not explain why Bergdahl left his platoon.
"There's nothing going on here that could justify in my mind or justify in anyone that I've talked to about this that would allow for or explain Bergdahl simply walking away and abandoning his post," retired Army Lt. Col. Tony Shaffer said.
While investigators continue to speculate about motivations, one common theme has emerged -- Bergdahl walked away.
CNN's Barbara Starr contributed to this report.