The shooting at a Christian school in Wisconsin may have been partly caused by bullying, cops said Tuesday — while officials added it’s too early to tell if the killer’s parents could be charged with a crime.

Madison Police Chief Shon Barnes told reporters at a press conference that investigators are still working to determine what exactly motivated 15-year-old Natalie “Samantha” Rupnow to open fire at the Abundant Life Christian School in Madison, killing a fellow pupil and a teacher before taking her own life.

“There are always signs of a school shooting before it occurs,” the police chief said.

“We’re looking into her online activity,” he said of Rupnow. “We’re asking for anyone who knew her or may have insight into her feelings leading up to yesterday’’ to come forward.

“On the question of bullying, we’re talking to students to understand whether bullying was one of those multiple factors that I mentioned earlier,” he said.

Barnes said the department is still working to determine the authenticity of a “manifesto” widely circulating online that’s been attributed to the shooter.

In the unconfirmed document, the writer says,  “I’ve grown to hate people, and society, it’s truly not my fault though, it never was. but all of you and the world have done to me is pick and tease me, you’ve pushed me into a corner with no help whatsoever.”

Questions remain how Rupnow managed to get her hands on the handgun used in the killings.

Wisconsin and federal law generally forbid anyone under the age of 18 from possessing a firearm.

Follow The Post’s coverage ofthe school shooting in Wisconsin

Madison Mayor Satya Rhodes-Conway noted that it was “far too early” to determine if Rupnow’s parents could wind up facing criminal charges, conceding, “We don’t know nearly enough yet.”

Barnes, addressing whether the shooter was targeting a specific person in her morning rampage, said, “Everyone was targeted in this incident, and everyone was put in equal danger.”

Rupnow shot up a room filled with study-hall kids ranging in ages at the K-12 school, authorities said.

The status of the six injured victims who were rushed to local hospitals after the shooting remained “unchanged,” he said. Two of the wounded teens are in “life-threatening” condition. The other four people wounded are a part-time teacher and three students.

The police chief clarified a widely reported claim that a 911 call reporting the shooting from inside the school had been placed by a second-grade student. In fact, he said, the call was made by a second-grade teacher.

In a bizarre moment near the end of the press conference, Satya Rhodes-Conway snapped at reporters when they asked questions about the victims.

“Alright, I’m going to say this, and then we are done: It is absolutely none of y’alls business who was harmed in this incident,” she claimed.

“Please have some human decency and respect for the people who lost loved ones or were injured themselves or whose children were injured. Just have some human decency, folks! Leave them alone. Let them grieve, let them recover. Let them heal. Don’t feed off their pain.”