A student at a Christian school in Madison, Wis., shot and killed a teacher and a fellow student on Monday in an attack that also left six people wounded, officials said.

The authorities said the shooter was a 15-year-old girl who apparently died of a self-inflicted gunshot. The victims, two of whom remained hospitalized in critical condition, have not been publicly identified.

The attack at Abundant Life Christian School took place during the last week of classes before Christmas break, and it sent emergency responders scrambling to the small, close-knit school on Madison’s east side. Much about the shooting remained unclear as investigators looked for a motive and detectives searched a home that they believed was connected to the attack.

Here’s what we know:

When did the attack happen?

A second-grader called 911 at 10:57 a.m. to report a shooting inside the school, Chief Shon F. Barnes of the Madison police said, and law enforcement officers began arriving three minutes later. He said officers immediately went inside and began searching for the shooter, who was found wounded at 11:05 a.m.

Audio that was archived online captured dispatchers scrambling to send emergency crews to the scene as the scope of the attack became clearer.