SHAWANO — Police in Shawano are investigating a written threat about a shooting at the school district.

Parents received an alert from the Shawano School District notifying them about extra patrols at area schools on Tuesday. According to police, a note detailing the threat was discovered written on a picnic table at a local park.

The note did not specify a date and did not say which school could be targeted within the district.

District officials say they are treating the threat seriously but remain unsure of the note’s credibility. An investigation is underway.