A gun control group is calling for the resignation of the southern Oregon sheriff who has led the response to last week’s mass shooting at Umpqua Community College in Roseburg.

Douglas County Sheriff John Hanlin, a staunch supporter of the Second Amendment, is under the microscope after a letter resurfaced that he had written to Vice President Joe Biden threatening not to enforce potential gun restrictions.

His esteem among gun control advocates suffered another hit following reports that he once shared a video on Facebook that suggested the U.S. government staged the 9/11 terrorist attacks and the Sandy Hook Elementary School shooting to “disarm the public.”

"This makes me wonder who we can trust anymore," he wrote on the since-deleted post. "Watch, listen, and keep an open mind."

Hanlin later distanced himself from these conspiracy theories, telling CNN on Friday, “That's not a conspiracy theory belief that I have."

Dan Gross, president of the Brady Campaign to Prevent Gun Violence, said in a statement Tuesday that Hanlin is incapable of investigating last week’s community college shooting.

"His conspiracy theories about 9/11 and Sandy Hook and his refusal to enforce the law not only violate his sworn responsibility as a sheriff, they also put a cloud over the investigation which he is charged with leading,” Gross said.

Slideshow: Deadly shooting at Umpqua Community College

“The public deserves to have the confidence that a thorough investigation is being conducted that will yield honest answers — not just the ones Hanlin deems should be shared.”

In an appearance on CNN, Gross doubled down on his critique of Hanlin as someone capable of handling the shooting probe.

“He is charged with leading an unbiased investigation into what happened and what can be done to prevent future tragedies,” Gross said. “And I think it’s extreme enough, that this guy is a 9/11 and Sandy Hook conspiracy theorist, to say that these are extenuating circumstances and to call for this guy's resignation.”

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Two weeks after Hanlin sent his letter to Biden, as the Brady Campaign points out, the National Sheriff's Association revealed its position that sheriffs have a responsibility to uphold laws that prevent or reduce access to firearms for “prohibited persons”: "Sheriffs do not possess the legal authority to interpret the constitutionality of any law."

But several Douglas County residents told the Los Angeles Times they disagree with the idea that the recent shooting underscores the importance of tightening gun restrictions, adding that most people in the area share Hanlin’s views.

"He's trying to protect everybody's Second Amendment rights," said Dennis Harper, who works at an auto parts store near the community college. "We're in Oregon; that's what we do."

Another local, Carolyn Kellim, who runs a gun shop out of her home, proudly described Douglas County as “hunting country,” adding that gun control would be "the worst thing in the world that can happen.”

Hanlin, who was born and raised in the Roseburg area, attended UCC. He enjoys hunting, fishing and riding his motorcycle through the county’s rural areas, according to his official biography.

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