According to the minutes from the arrest hearing, the man must have sent a letter to a police chief in Örebro.
The letter begins with the words "Hello, one of the government officials".
The letter states that the man intends to "studied and systematically execute 12 randomly selected persons", according to the minutes.
After the incident, the man was arrested for making a serious threat to an official.
But now the prosecutor has decided to close the preliminary investigation.
P4 Örebro reports that the reason is that the Court of Appeal found that the letter that was sent is not criminal.
SVT Nyheter Örebro has sought the prosecutor.