From the article:
The agents are searching for some of their own retired service weapons as well as guns from other federal law enforcement agencies, including the FBI and DEA. All of the weapons had been sent to the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives' National Firearms and Ammunition Destruction Branch in Martinsburg, West Virginia, to be shredded, according to court documents and congressional letters.
But, WHY shred them? That doesn’t make sense.