Michelle Jokisch Polo

The National Weather Service has extended an Air Quality Alert for more than 20 Michigan counties through Thursday.

Michigan State University plans to return to classes on Monday, nearly a week after a gunman shot and killed three students and wounded five. One of the students hospitalized is stable, while four others remain in critical condition.

Every member of the department resigned last week, saying the city has failed to communicate effectively with them.

A flood of threats has followed Michigan's school shooting. Information about missed warning signs has spurred a conversation about threats and how to reassure families that classrooms are safe.