Agent Kevin Kelm, with the Bureau of Alcohol, Tobacco, Firearms and Explosives, says police were called to Birkhead's home when a social worker sent to check on the well-being of Birkhead's daughters heard that he was acquiring weapons.
On Thursday, the 52-year-old pleaded guilty in U.S. District Court in Owensboro to possessing and manufacturing explosive materials without a license.
He is scheduled to be sentenced on March 4. The government has recommended a six- to 12-month sentence.
