A grizzly bear attacked a group of students and teachers in the Bella Coola Valley of British Columbia’s Nuxalk Nation on Thursday, leaving two people critically injured and two others seriously hurt.

The attack occurred when the group stopped along a trail near a river and a bear suddenly emerged from the forest.

Teachers intervened using bear spray and a bear banger to drive the animal away, and the bear remains on the loose as conservation officers continue search efforts.

Local authorities and Nuxalk Nation leadership have urged residents to stay indoors and avoid nearby forests, rivers and trails, CBS News has reported.

Acwsalcta School, which serves the community, closed Friday and said it will provide emotional support for students and staff affected by the traumatic event.