Two teenagers at a Glendale, AZ high school were killed Friday morning in a shooting that police are calling a tragic situation.

Glendale police spokesperson Tracey Breeden said officers responded to several 911 calls of a shooting at Independence High School near 75th and Glendale avenues just before school was to start at 8 a.m.

Police found two 15-year-old female sophomores lying next to each other on campus, each dead from a single gunshot wound, said Breeden. A weapon was found next to them.

Teacher Phuong Kieu talked to ABC15 Friday afternoon and identified her sister May as one of the victims. Police have not yet confirmed the victims’ identities.

The circumstances of what led to the shooting are still under investigation, and the relationship between the two girls was not immediately clear.

Police referred to the situation as an “isolated incident,” and were quick to reassure parents that their children “are safe” and that this was not an active shooter-type situation.