The Abundant Life Christian School remains a crime scene Thursday as detectives search for a motive in the deadly Monday morning shooting carried out by a student and probe her possible links to a man who – according to an Associated Press report – authorities believe was planning another mass shooting in California.

The campus remains closed as investigators comb through social media and documents to understand how 15-year-old Natalie Rupnow, who went by Samantha, got a firearm used in the killings at the private school in Madison, Wisconsin.

Rupnow used a handgun to carry out the attack, authorities said. The handgun and a second gun not used in the attack were found at the scene, Madison police said Wednesday. The US Bureau of Alcohol, Tobacco, Firearms and Explosives has traced the origins of the weapons, but police won’t provide further information on the guns, “as it could jeopardize our investigation,” a police statement said.

Teacher Erin Michelle West, 42, of DeForest, and student Rubi Patricia Vergara, 14, of Madison, were both pronounced dead at the scene, the Dane County Medical Examiner’s Office said in a news release Wednesday.

Six people were injured. Two students with life-threatening injuries remain hospitalized, while four other people with minor injuries were discharged, the Madison Police Department said in a release Wednesday.

The tragedy is one of more than 80 school shootings across the United States this year – surpassing 2023 for the most in a single year since CNN began tracking such incidents in 2008.

Rupnow was pronounced dead at a hospital Monday as a result of “firearm related trauma,” the medical examiner’s office said, noting additional testing is underway.

Data from an FBI study and other reports suggest that active shooter incidents involving female shooters are rare. CNN has documented 83 school shootings in 2024, and of the 59 in which the gender identity of the suspected shooter was available, only two were female.

As investigators sift through Rupnow’s social media and analyze documents she is purported to have written, it also appears she had been in contact with a 20-year-old man in Carlsbad, California, who was plotting a mass shooting with the teenager and told her he was planning to attack a government building, the AP reported, citing court documents.

A California judge issued a restraining order against the man Tuesday under California’s red flag law, the AP reported. The order requires the man to turn his guns and ammunition within 48 hours unless an officer asks for them sooner.

CNN has reached out to Carlsbad police and the FBI for information.

Rupnow’s parents, Jeff and Mellissa Rupnow, have not responded to CNN’s repeated requests for comment. They are cooperating with police, Madison Police Chief Shon Barnes has said.

Court records obtained by CNN show Rupnow’s parents have been married to each other and divorced from each other twice, with court orders requiring the teen to split time between her mother’s home and her father’s.

The mayor of Madison said it is too early to comment on whether the parents of the shooter will face criminal charges, as have a few other parents of US school shooters in recent years. Investigators are looking at “if the parents may have been negligent,” Barnes said Tuesday. He also said investigators “have no reason to believe that they have committed a crime at this time.”

Jeff Rupnow had posted a photo on Facebook of his daughter at a shooting range in August. In the photo, the teenager can be seen wearing a black shirt with the name of the band KMFDM, whose lyrics were cited by the students who carried out the 1999 massacre at Columbine High School in Colorado, where 13 people were killed.

KMFDM issued a statement condemning the 1999 attack and expressed sympathy for the victims, adding their music was intended to stand against violence, according to Reuters.

In October, a Georgia grand jury indicted a father on murder and other charges in the mass shooting by his son at Apalachee High School in Winder, Georgia, as the nation continues to struggle with accountability for the violence plaguing American schools.

Police in Wisconsin are also talking to Abundant Life Christian School students to determine whether bullying was one of the factors in Monday’s shooting, Barnes said.

Mackynzie Wilson, a sophomore at the school who had a locker next to Rupnow’s, said she never thought the student she described as shy would be capable of carrying out an act of such violence.

“She was really quiet. She didn’t really have any friends, and she just seemed really lonely,” Wilson told CNN. “It wasn’t like she was trying to fit in. She seemed very content being alone.”

Students described West, a teacher employed part-time by the school, as a loving person who devoted her time to supporting them.

Angel Brube, a seventh-grader at the school, told CNN he knew the teacher well and described her as “always very kind and caring” and “a really good person,” he told CNN

“She really loved her kids, and she really, really loved everyone at our school, and she would have done anything for them,” Wilson said.

Vergara, a freshman at the school, was an animal lover who was passionate about art, reading and playing music, according to her online obituary at Gunderson Funeral Home.

“She was an avid reader, loved art, singing and playing keyboard in the family worship band,” her obituary reads. “She shared a special bond with her beloved pets, Ginger (cat) and Coco (dog).”

West and Vergara died of “homicidal firearm related trauma,” preliminary autopsy results found. The medical examiner’s office said it will be conducting additional testing.

Residents and officials call for action

Hundreds gathered outside the Wisconsin State Capitol on Tuesday night to remember victims. A Christmas tree twinkled as mourners met in freezing temperatures to grieve, holding candles and hugging therapy dogs.

For students like Wilson, it was difficult returning to the school for the vigil because of the “fear and trauma that built up,” she said.

Madison local Justin Myers brought his two young children to the Tuesday vigil, telling CNN he had “told them the truth” about what happened at Abundant Life.

“It’s an epidemic, and I’m not a big believer in the thoughts and prayers crap –– I don’t think it works,” he added. “We need action, legislation and laws to make sure that guns don’t get into the hands of people who don’t have them.”

President Joe Biden, Vice President Kamala Harris and Wisconsin Democratic Rep. Mark Pocan called for more action from Congress to address gun violence.

“From Newtown to Uvalde, Parkland to Madison, to so many other shootings that don’t receive attention – it is unacceptable that we are unable to protect our children from this scourge of gun violence,” Biden said in a statement Monday.

Existing Wisconsin law limiting gun access to children is not sufficient, Dane County Executive Melissa Agard said Tuesday. “Our laws in Wisconsin are far too lax when it comes to access of guns by children,” Agard said Tuesday.

“We should have background checks. We should have red flag bills, we should be providing adequate support for everyone in our community when it comes to behavioral health,” Agard added.

Both federal and Wisconsin law generally make it illegal for someone younger than 18 to possess a firearm. State law similarly makes it illegal for any person to intentionally sell, loan or give a dangerous weapon to someone younger than 18 –– but there are exceptions such as allowing minors to possess a firearm for target practice under adult supervision, for use in the armed forces or for hunting.

Wisconsin also has a child access firearm law that makes it illegal to recklessly store a loaded firearm within reach or easy access of a child younger than 14.

CNN’s Taylor Romine, Sarah Dewberry, Elise Hammond, Holly Yan, Steve Almasy, Jillian Sykes, Caroll Alvarado, Whitney Wild and Taylor Galgano contributed to this report.