A 15-year-old girl opened fire Monday at Abundant Life Christian School in Madison, Wisconsin, killing a teacher and a student and wounding six others at the school she attended, police said.

The suspect, Natalie Rupnow, was also dead, police said. There is evidence that the teenager, who called herself Samantha, died of a self-inflicted gunshot wound.

The teenage suspect used a handgun, police said. Authorities are investigating the source of the gun and searching Rupnow’s home on the city’s north side, Madison Police Chief Shon Barnes said.

A motive is unclear, Barnes said at a news conference.

It is also unclear whether any of the victims were targeted, officials said Monday.

The suspect’s father reportedly spoke to police at one of their facilities.

Police are “trying to figure out what he knew or didn’t know about what happened today, but again, he lost someone,” Barnes said.

Barnes also said police do not currently plan to charge Rupnow’s parents in connection with the fatal shooting.

“The parents are cooperating fully. We have no reason to believe at this point that they committed a crime,” Barnes said.

“This has obviously shocked our school community,” said Barbara Wiers, director of elementary and school relations at Abundant Life Christian School. “But we know it affects not only our school community, but also Madison and the surrounding area and all schools.”

The shooting took place shortly before 11 a.m. in a mixed-age and mixed-year classroom.

A second grader called 911.

“Let that sink in for a minute,” Barnes said. “A second grader called 911 at 10:57 a.m. to report a school shooting.”

The school does not have metal detectors or a school resource officer, but does have other safety protocols in place, including cameras, Wiers said.

“We had retraining before the start of the school year. We train for that. We are conducting lockdown drills, we are conducting evacuation drills as part of our standard drill protocols. Our students are familiar with this. Our teachers are very familiar with this,” she explained. “The training we did with (Madison Police Department) right at the beginning of the year before students returned to campus had some innovations in it, and so we had looked at some of those things. So I think everything was very fresh for our faculty.”

“I can’t tell you how well our students did in this process. They were visibly scared when they realized that when we practice we always say, ‘It’s a drill, it’s just a drill.’ When they heard “lockdown, lockdown” and nothing else, they knew it was real,” Wiers said, adding, “But they did brilliantly.”

Two students were in critical condition with life-threatening injuries, Barnes said, while another three students and a teacher suffered non-life-threatening injuries.

Two of the four injured were released from SSM Health St. Mary’s Hospital – Madison Monday evening.

Officers responded to an active shooter report around 10:57 a.m

The suspect was dead when police arrived and no officers fired their weapons, Barnes said.

The shooting was “confined to one room,” but it was not clear whether it was a classroom or a hallway, the chief said.

The police assume that the suspect was already at the school and there was no break-in.

“I’ve never seen so many police cars in my life – just blue and red lights lining the school and the streets. Firefighters, paramedics, everyone was there,” John Diaz De Leon told ABC News Live in the normally quiet area.

He said he saw officers with long guns at the scene and older students running from the school across the parking lot.

“Later, the younger students were let out, very slowly and more orderly, holding hands, to walk across the parking lot,” he said.

The school was evacuated, Barnes said. There is no danger to the community, he said.

The suspect’s family is cooperating, the police chief said.

Investigators are looking into whether there were any possible warning signs, Barnes said.

All students were reunited with their parents by Monday evening, Barnes said. About 390 students from kindergarten through 12th grade attend the private school.

“We hope something good comes out of this as we learn and grow and can continue to support other schools,” Wiers said.

She thanked first responders for their support and said the school community is leaning on their faith during this time.

President Joe Biden called the incident “shocking and incomprehensible” in a statement Monday evening, calling on Congress to act “now.”

He insisted they pass “common sense” gun safety laws, including universal background checks, a national red flag law and a ban on both assault weapons and high-capacity magazines.

“It is unacceptable that we cannot protect our children from this scourge of gun violence,” the statement said, adding: “We cannot continue to accept it as normal.”

Biden also noted his administration’s efforts to combat the gun violence epidemic in the United States, including the creation of the White House Office to Prevent Gun Violence, said more needs to be done and offered his prayers to those affected in Madison.

Madison’s police chief said he began his career as a teacher.

“We owe it to our community to do everything we can to ensure that schools are not only a special place, but a safe place,” he said.

“I hoped this day would never come in Madison,” said Madison Mayor Satya Rhodes-Conway.

She emphasized the need to prevent gun violence and said she wants the community and country to ensure that “no officer ever has to stand in this position again.”

Jill Underly, Wisconsin’s public education director, also emphasized the need for change, saying in a statement: “This tragedy is a stark reminder that we must do more to protect our children and our educators to ensure that “Such horrors will never happen again.” We will not rest until we find solutions that make our schools safe.”

Wisconsin Gov. Tony Evers said in a statement, “There are no words to describe the devastation and heartache we feel,” calling the shooting a “harrowing tragedy.”

Evers said he and his wife are praying “for the families and loved ones of those whose lives were so senselessly taken, as well as for the educators, staff and the entire Abundant Life school community.”

“It is unthinkable that a child or a teacher would wake up one morning, go to school and never come home again,” he said. “This should never happen, and I will never accept this as a foregone conclusion or stop working to change it.”

This is a developing story. Please check back for updates.