The U.S. Attorney for Northwest Indiana said Krieg, an engineer, is currently in federal custody and is facing charges of knowing possession of a destructive advice and transporting explosive materials. He faces a maximum of 10 years in prison on both counts.
According to prosecutors, Krieg was responsible for the explosion at the East Chicago Post Office in the 900-block of East Chicago Avenue on Sept. 6. The U.S. Attorney said Krieg tried to mail a device that resembled a pipe bomb to a local resident. The makeshift bomb detonated at the post office.
Then, a few weeks later, investigators said another alleged victim received a threatening letter from Krieg that contained a bullet.
Prosecutors said Krieg was arrested at his home in Munster by federal authorities Thursday morning.
The U.S. Postal Inspector said the postal worker injured in the pipe bomb explosion was seven months pregnant at the time, but suffered only minor injuries and has recovered.