From the article

Six states allow citizens to petition a district court directly for a criminal grand jury: Kansas, Nebraska, Nevada, New Mexico, North Dakota, and Oklahoma. The petition goes to the district court. The judge’s only two questions are whether there are enough valid signatures and whether the conduct, if true, is a crime under state law. No district attorney or attorney general has any part in it.

The article spells out specifically how citizens of these states can help initiate an actual prosecution, and includes links to get people started.