A suspected student gunman and a school resource officer at a Wisconsin high school exchanged gunfire Monday morning before the suspect was taken into custody, according to officials.

The Waukesha Police Department said at about 11 a.m. that there had been a “critical incident” at Waukesha South High School, but added that the building was “safe and secure.” Waukesha is about 15 miles west of Milwaukee.

A suspect had been taken into custody, and no other suspects were being sought, police said. “This is an isolated incident,” the department said in a tweet. “We are in the investigative stage right now as the scene is stabilized.”

A district spokesperson told NBC affiliate TMJ that the student who exchanged gunfire with the school resource officer had been struck. His condition was not immediately known.

A message sent to students’ parents said the school had been placed on lockdown as police responded to the incident. The message said students would be released at 11:15 a.m.

This is a developing story, please check back for updates.