Wisconsin police said an officer shot an armed male student at Waukesha South High after the suspect refused to disarm and pointed his gun at officers.
Oshkosh parents were advised to reunite with their children at Perry Tipler Middle school.
Officials said the student and resource officer were taken to local hospitals but did not say how badly they were injured.
Police believe the teen wrote the message with the knowledge of one of their friends as part of a trend on the social media app TikTok, according to the release.
Other officers responded and tried to start a dialogue with the suspect, Jack said.
Oshkosh police have turned over the incident to the State Department of Criminal Investigations.
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Oshkosh West High School, about 137km north of Milwaukee, was put on lockdown after the altercation, Oshkosh Chief of Police Dean Smith said during a news conference. The 17-year-old boy was wounded and is in custody in stable condition.
On Monday, about 80 miles away from Oshkosh, a student brought a gun to Waukesha South High School in Waukesha, Wisconsin, according to police. The student and the officer were taken to hospitals, but no one else was injured, Mann said.
The state Justice Department's office of school safety was working with both schools in Oshkosh and Waukesha to provide them with any services they may need, Kaul said.
School shootings have occasionally shone a spotlight on the response by guards and school resource officers.
The school resource officer "was forced to discharge" his firearm and officers immediately administered life-saving attention to the student.
The incident occurred just a week after a threat of school shooting was found on a bathroom mirror at Laguna Middle School.