Wisconsin school shooting: Police to give update on deadly shooting investigation | LIVE

MADISON, Wis. -- Details are still emerging about the course of the Madison, Wisconsin, school shooting that left three people -- among them the 15-year-old female shooter -- dead and several others injured on Monday.

Police said that Natalie Rupnow, who went by Samantha, used a handgun to kill one teacher and one fellow student in the shooting.

Rupnow died of a self-inflicted gunshot wound before officers reached the school, police said. Officers did not fire their weapons.

Two students sustained life-threatening injuries and are in critical condition, while one teacher and two other students were treated for non-life-threatening injuries.

Some of the injured are now out of the hospital, but two students remain in critical condition with life-threatening injuries.

Police said in a Monday briefing that the shooting was contained to "a classroom in a study hall full of students from multiple grade levels."

Police have not yet suggested any motive for the attack nor said whether they believe the victims were specifically targeted.

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Devastated staff at Abundant Life Christian School returned to the scene Tuesday morning.

A group of bus drivers and school monitors brought flowers and candles to create a memorial, saying a prayer for the lives lost.

"This is a good town and for something like this to happen up here, I've never been to a town or city or nothing like this happened," school bus driver Kamila Reynolds said.

Squad cars and crime tape blocked off the building where a 15-year-old girl opened fire inside her own school Monday.

Student Nora Gottschalk heard the shooting:

"We went to the church right next to my school and everyone was panicking still because a lot of police were there," she said. "A lot."

A second-grader made the 911 call, Madison Police Chief Shon Barnes said. "Let that soak in for a minute," Barnes added. "A second-grade student called 911 at 10:57 a.m. to report a shooting at school."

Officers swarmed the building within three minutes. But the shooting - that took place in a classroom full of study hall students was over by the time police got there.

"We always send prayers," mother Mireille Jean-Charles said. "We always send thoughts. When are we going to stop doing that? This is not OK."

Police said the teen suspect Natalie Rupnow who went by the name Samantha died of a self-inflicted gunshot wound.

Video shows police searching her home Monday. Madison Chief Shon Barnes provided an update on the Search Tuesday morning.

"Detectives and investigators were out there late last night, pulling things from the home, looking at papers and effects," Chief Barnes said. "So hopefully we have an opportunity to analyze some of that. Perhaps put a piece together to figure out why this happened in our city."

He said the teen's family has been cooperating with detectives.

Authorities said the suspect used a handgun in the mass shooting. How she got the gun or had access to it - is still unknown as is the motive and intention behind the killings.

"They probably have more questions than anyone because they knew her they lived with her and so we wanted to get an account from them of what kind of child she was, what was going through her mind maybe at the time, what kind of day she have that morning," Chief Barnes said.

Chief Shon Barnes said Monday, "I don't know whether [the shooter] was transgender or not," adding that the speculation as to Rupnow's background was of no consequence to authorities at the time.

"I don't think that whatever happened today has anything to do with how she or he or they may have wanted to identify," Barnes added.

The suspect's father reportedly spoke with police at one of their facilities shortly after the incident. Police are "trying to determine what he knew or may have not known about what happened today, but again, he lost someone as well," Barnes said.

"The parents are fully cooperating, we have no reason to believe that they have committed a crime at this time," Barnes said.

President Joe Biden called the incident "shocking and unconscionable" in a statement Monday evening that called on Congress to act, "now."

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

ALSO SEE: What to know about Natalie Rupnow, the 15-year-old suspected school shooter in Wisconsin

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

Biden also mentioned his administration's efforts to combat the gun violence epidemic in the United States, including the implementation of the White House Office of Gun Violence Prevention, while stating that more needed to be done and offering his prayers to those affected in Madison.

Wisconsin Gov. Tony Evers said in a statement, "There are no words to describe the devastation and heartbreak we feel," calling the shooting a "gut-wrenching tragedy."

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

"It is unthinkable that a kid or an educator might wake up and go to school one morning and never come home," he said. "This should never happen, and I will never accept this as a foregone reality or stop working to change it."