An Iowa man who mailed bomb threats to the FBI office in Omaha has been sentenced to time served. Thirty-year-old Matthew Fell, of Waterloo, Iowa, was sentenced on Wednesday in Lincoln by Senior U.S. District Judge Richard Kopf. Fell had pleaded guilty to making a false threat. Fell has been behind bars for 15 months while awaiting final disposition of his case. Court documents say postal workers at a Lincoln post office found an envelope in June 2012 that had, "This is a Bomb!" written on it. There was no bomb in the envelope, but it did contain another envelope that was addressed to the FBI in Omaha. That envelope contained a piece of paper and a thumb drive. Omaha postal workers found a similar envelope a week later.