Police in the US state of Wisconsin said the 911 call they received about Monday’s school shooting came from a child no older than seven or eight years old.

A teenage student and a teacher were shot and six others were injured at a private Christian school by a 15-year-old girl named by authorities as Natalie Rupnow. The attacker, who attended the school, was also found dead with a pistol.

The Madison police chief said the child, who called 911 shortly before 11 a.m. local time (5 p.m. GMT), was in second grade. “Let that sink in for a minute,” Shon Barnes told reporters.

The attacker’s motive is still unclear. The next police press conference is expected on Tuesday afternoon.

The names of the victims are not yet known, nor is the child who raised the alarm.

Chief Barnes said two students are facing life-threatening injuries. Four other people were taken to hospital and two of them were later released.

The attacker, who also used the first name Samantha, is believed to have died of a self-inflicted gunshot wound. No officers fired shots.

She visited the school before launching the attack Monday, Chief Barnes said. The shooting was confined to a classroom with mixed-grade students.

When asked about a text posted online that purportedly was written by Rupnow, Chief Barnes said, “We have not been able to verify that it is authentic. We are certainly aware that it was published and that the person who published it also allegedly did so.” Information has been shared with the FBI, he added.

Rupnow’s family has cooperated with the investigation. Local media reported that a property north of Madison was searched Monday.

Authorities have also asked to hear from witnesses, and some of those present at the attack on Abundant Life Christian School have spoken to local media.

Nora Gottschalk, eight years old, told CNN affiliate WISC that she was getting ready for lunch when the shots rang out. She saw an injured teacher screaming for help. “I was really scared and really sad,” she said.

Adler Jean-Charles, who is in sixth grade, said he heard two gunshots in English class. “Some people started crying and then we just waited for the police to come,” he told WISC.

Bethany Highman, who attended the school and now has a daughter who is a student, told another CNN affiliate, WMTV: “I pray with my children every morning that this doesn’t happen, and this is the world we’re in life.”

The school’s director of relations said students’ preparation for a mass shooting was “very fresh” following sessions earlier this year.

President Joe Biden said the shooting was “shocking and irresponsible” and urged lawmakers to immediately enact legislation that could prevent more gun violence.

Mass shootings are commonplace in the USA, including at schools. According to the news organization EducationWeek, 38 of them have caused deaths or injuries this year. Before Monday’s attack, there were a total of 69 victims – including 16 deaths.

But school shootings by female attackers are rare.

The school, which has around 400 students from kindergarten through high school age, will remain closed during the investigation.