Daniel Sheehan, of Deer Park, was convicted by a federal jury and faces 30 years in prison. He had been charged with attempted extortion and the use of a destructive device.
Prosecutors say Sheehan sent an anonymous letter to the manager of a Home Depot store in Huntington last October. The letter said a bomb had been planted there.
Authorities later found a device and detonated it.
Prosecutors say the 50-year-old Sheehan later threatened to set off three more bombs on Black Friday if he didn't get $2 million.
Sheehan's defense attorney denied that the device left in the Huntington store was dangerous.
