The blast killed Kendall, 56, of Columbia, and Kennett, 49, of Stratford, and injured David Oldham, of Columbia, who was also injured in a flash explosion at the same Black Mag plant several months before, in January 2010.

According to the New Hampshire Fire Marshal's office, there were possible violations of state statute in the handling, manufacturing and storage of gunpowder at the plant, violations of general fire safety and indications the fatal blast might have occurred during the manufacturing process.

In June 2011, Black Mag entered into an agreement with the U.S. Labor Department that resolved more than 50 workplace safety and health violations issued by the Occupational Safety and Health Administration (OSHA) with penalties totaling $1.2 million.

The agreement requires Sanborn to surrender his explosives manufacturing license and permanently refrain from employing workers in explosives-related businesses.

The federal lawsuits brought by the families of Kendall and Kennett allege that Sanborn as well as the other co-owners of the building that housed the Black Mag plant failed to take adequate safety precautions and remedial measures in response to the January 2010 flash explosion.

In addition to Millennium Designed Muzzleloaders, the other defendants named in the civil suit are Rex and Karen Jacobsma and Driver Limited Partnership.