Officials are trying to determine why a 15-year-old girl allegedly opened fire at her school, Abundant Life Christian School, on Monday morning, killing a fellow student and teacher. This was a heinous crime that shocked the community of Madison, Wisconsin.

The motive appears to be a combination of factors, Madison Police Chief Shon Barnes said at a news conference Tuesday.

Police are talking to students to determine whether bullying is a factor, he said.

“Everyone was targeted in this incident and everyone was equally at risk,” Barnes said.

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

A candlelight vigil for the shooting victims was held in the state capital on Tuesday evening.

“Yesterday, the Madison community experienced a horrific and traumatic event,” Madison Mayor Satya Rhodes-Conway said at the vigil. “We will never be the same, but we will get through this. And we will get through this together, relying on each other and taking care of each other.”

The victims have not been publicly identified. Rhodes-Conway told reporters during the news conference that they will respect the privacy of the victims’ families and “will share what we can, when we can, and not before.”

“Let them grieve. Let her recover. Let them heal,” she said.

The suspect, Natalie Rupnow, who called herself Samantha, died of a self-inflicted gunshot wound, police said. The officers did not fire their weapons.

Police are investigating Rupnow’s online activities, Barnes said. He urged anyone who knew her or had insight into her feelings to call Madison Area Crime Stoppers at 608-266-6014.

Rupnow’s parents are cooperating with the investigation, Barnes told ABC News on Tuesday.

“They were cooperative. Despite this tragedy, they still lost a child. They still lost a family member,” Barnes said. “It’s safe to say that they probably have more questions than anyone else because they knew her. They lived with her and so we wanted to get a report from them about what kind of child she was.”

Her father is being interviewed by investigators, Barnes said. He said he didn’t know if the mother had been interviewed, noting she had been out of town.

Students from kindergarten through 12th grade attend the Christian school. Police said the shooting occurred in a classroom while a study hall was “full of students of various grade levels.”

“I was in the hallway and was about to change my shoes into boots to go to lunch because I have a break afterward, but then I heard gunshots and screaming,” a second-grade girl told Chicago’s ABC -WLS transmitter.

A second-grade teacher called 911 at 10:57 a.m., Barnes said.

Police initially said Monday it was a second-grader who called 911; On Tuesday, Barnes changed that to a teacher.

James Smith told ABC News his 17-year-old daughter was in physics class when shots were fired two classrooms away. She wasn’t hurt.

Smith said Abundant Life Christian School welcomes students who may have been bullied or had a difficult time at other schools.

“As a school, we want to help those who are struggling and provide them with a safe space to grow while also creating a safe space for the rest of our student body,” he said.

Smith also said the school population grew dramatically after the pandemic as many parents sought an alternative to public schools.

On Tuesday, numerous schools in the Madison Metropolitan School District “became the target of false threats, often known as swatting,” Barnes told reporters.

Police are investigating, Barnes said, noting that authorities do not believe there are any threats at this time.

“Making false threats is a crime and we are cooperating with the prosecutor,” he said.

In the wake of Monday’s shooting, President Joe Biden and Vice President Kamala Harris are calling on elected officials to combat gun violence.

Biden called the shooting “shocking and irresponsible” in a statement and cited his administration’s efforts to combat the gun violence epidemic in the U.S., including the implementation of the White House Office of Gun Violence Prevention.

Biden called on Congress to 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,” Biden said, adding: “We cannot continue to accept it as normal.”

“It’s another school shooting, another community torn and torn apart by gun violence,” Vice President Kamala Harris said in a statement Tuesday. “And of course our nation mourns those killed, and we pray for the recovery of those injured and for the entire community.”

Harris, who played a role in the Biden administration’s efforts to combat gun violence, emphasized: “We as a nation must renew our commitment to ending the horror of gun violence, both mass shootings and everyday gun violence, that affects so many communities across our country regards.” .”

“We need to end it, and we need to have the courage to know that solutions are at hand, but we need elected leaders who have the courage to step up and do the right thing,” she said.

ABC News’ Alex Perez, Briana Stewart and Molly Nagle contributed to this report.