A North Carolina man admitted mailing 50 homemade M-80 explosive devices to a friend in Prince William County, Virginia.
According to prosecutors, the devices were crudely made and contained explosive components, plastic caps and liquids.
They were intercepted by postal workers in Gainesville, Virginia, who had spotted suspicious tubes and wires inside the mail parcel.
The devices were at risk of exploding and killing postal workers if mishandled or dropped, according to court testimony Friday.
Lanford Parrott pleaded guilty to a federal offense and acknowledged his conduct was outrageous.