Madison, Wisconsin - A 15-year-old female student was identified by police as the shooter who opened fire Monday at a Christian school in Wisconsin, killing a fellow student and a teacher, as well as herself.

Shon Barnes, police chief in the state capital Madison, told a press briefing that three people had died and seven others were wounded at the Abundant Life Christian School, a private Christian school with about 400 students.

"The shooter has now been identified as (a) 15-year-old," Barnes told reporters, identifying the minor by name.

"She was a student at the school, and evidence suggests she died from a self-inflicted gunshot wound," he added.

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Of the six wounded victims who were hospitalized, two students remain in critical condition with life-threatening injuries, two people are in stable condition, and two have been discharged from hospital, the police chief said.

A handgun was recovered at the scene, Barnes said, adding that the suspect's family was cooperating with the police investigation.

"We are still working to determine a motive," he said.

The shooting, which was first reported to police by a second-grader per Barnes, happened in the final week of classes before students head to Christmas holidays, said Barbara Wiers, the school's director of elementary and school relations.

"This has obviously rocked our school community," she told a media briefing, saying it was not yet decided if students would return before the year-end break.

One witness interviewed by local media said they had heard two gunshots during the attack.

"We heard them and then some people started crying and then we just waited until the police came and then they escorted us out to the church," said the child, who was not identified.

Barnes some medical personnel responding to Abundant Life came directly from training for a mass shooting.

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"I think we can all agree that enough is enough," Barnes told reporters. "We have to come together to do everything we can to support our students, to prevent press conferences like these from happening again and again and again."

President Joe Biden condemned the shooting as "shocking and unconscionable" and said the tragedy underscored yet again the need for tighter gun laws.

"It is unacceptable that we are unable to protect our children from this scourge of gun violence. We cannot continue to accept it as normal," he said in a statement.

"We need Congress to act. Now."

This year, there have been at least 487 mass shootings – defined as a shooting involving at least four victims, dead or wounded – across the US, according to the Gun Violence Archive.

At least 16,012 people have been killed in firearms violence in the United States this year, not including suicides, GVA reported Monday.