On Monday, a 15-year-old female student, who has now been identified as Natalie Rupnow, reportedly entered a Christian private school in Madison, Wisconsin with a gun and started shooting.

The incident left two dead including a staff member and another student, as well as six others injured.

Two of the people injured remain in critical condition in hospital.

Rupnow, who was also known as ‘Samantha’ according to the authorities, was found dead when officers responded to Abundant Life Christian School with evidence suggesting that the alleged shooter died of a self-inflicted gunshot wound.

Crime scene tape continues to be stretched around Abundant Life Christian School as police continue to investigate Monday’s shooting. Credit: Scott Olson/Getty

While a close-knit community mourns the loss of two innocent lives, Madison police are in the process of examining Rupnow’s background and motive for the attack.

Here’s what we know so far.

The shooter used a handgun to carry out the attack.

The Bureau of Alcohol, Tobacco, Firearms and Explosives is tracing the weapon back to its initial location before it came into the possession of the teen, police said.

“We have asked our partners with the ATF to expedite what’s called an ATF trace form to try and determine the origin of that weapon, who purchased it, and how it got from a manufacturer all the way to the hands of a 15-year-old girl,” Madison Police Chief Shon Barnes told CNN News Central on Tuesday. “These are questions that are going to take some time to answer.”

It is not yet clear who owns the gun, but the outlet also reported that the shooter was seen at a shooting range with her father back in August wearing a T-shirt with the name of the band KMFDM.

The German rock band’s lyrics were cited by the students who carried out the 1999 massacre at Columbine High School in Colorado, where 13 people were killed as a result.

Reuters reported that KMFDM had issued a statement at the time condemning the attack, emphasizing their music was not intended to incite violence.

People leave messages on crosses during a vigil on the grounds of the state Capital building to mourn the victims of the shooting at Abundant Life Christian School . Credit: Scott Olson/Getty

Rupnow’s parents are cooperating with the authorities.

Rupnow was said to have had “a turbulent home life,” as per court records, “which show that her parents divorced and remarried multiple times and that she had been enrolled in therapy,” the Washington Post reported.

“A Washington Post review of court records points to an unsettled childhood for Rupnow, whose parents’ custody agreements sometimes forced her to move between their homes every two or three days,” the outlet confirmed.

Together with the district attorney’s office, the police will be aiming to “look at if the parents may have been negligent,” he said. “But at this time, that does not appear to be the case.”

Police stand guard outside the home of 15-year-old Natalie “Samantha” Rupnow after she killed two people at school in Wisconsin. Credit: Scott Olson/Getty

The police’s top priority at the moment is finding out the shooter’s motive.

During the news conference on Tuesday, Barnes doubled down on finding out the shooter’s initial motive behind the attack.

“… At this time, it appears that the motive was a combination of factors,” he said, though he did not clarify any further details.

The authorities are also speaking to students to determine if bullying was one of them, Barnes said.

“Some have asked if people were specifically targeted. Everyone was targeted in this incident, and everyone was put in equal danger,” he added.

The chief also noted that there has been wind of a “document” that had “been widely shared on social media.”

“At this time we cannot verify its authenticity,” the chief said. “We have detectives working today to determine where this document originated, and who actually shared it online.”