The Arizona attorney general's office said Wednesday that a grand jury indicted Jeffrey Metcalf last week on 42 counts of misconduct involving weapons.
Authorities say a task force discovered bomb-making materials in Metcalf's car during a traffic stop last month. That led to a search of the former Marine’s home.
Department of Public Safety officers found 41 homemade pipe bombs in a cooler and one in the backyard.
The Associated Press says a message left with a defense attorney listed for Metcalf in court records was not immediately returned.