News Update: Wisconsin School Shooter May Have Plotted With…..Read more

Law enforcement officials grew concerned this week that the Wisconsin school shooting on Monday may have been part of a broader plot that could have included an attack on a government building, according to a court document filed in California.

As F.B.I. agents pursued leads after the shooting at Abundant Life Christian School in Madison, they found messages that the shooter, Natalie Rupnow, 15, exchanged online with a 20-year-old man in the San Diego area, according to the document.

Agents detained and questioned the man on Tuesday. The man told investigators that “he told Rupnow that he would arm himself with explosives and a gun and that he would target a government building,” an officer from the Carlsbad Police Department wrote in a document seeking a judge’s permission to seize any weapons in the man’s possession.

The petition said F.B.I. agents reviewed messages between the Wisconsin shooter and the California man. The document did not say how the two communicated, and it did not provide additional details about their correspondence.

The California man does not appear to have been charged with a crime in connection with the shooting. Denise Ramirez, a spokeswoman for the Carlsbad Police Department, said in an email that city officials were helping the F.B.I. in its investigation. She added: “We do not believe there to be a threat to our city.”

Caroline Clancy, a spokeswoman for the F.B.I. in Wisconsin, said in a statement the agency was not aware of any ongoing threats in Wisconsin or California related to Monday’s shooting.

Judge Laura Duffy of the Superior Court of San Diego County granted the request to compel the man to surrender any weapons to law enforcement officials within 48 hours. A court hearing on the case was scheduled for Jan. 3.

The request was filed under a legal provision intended to disarm people who may pose a threat to themselves or others. Law enforcement officials and relatives of someone with access to firearms can request a judge to order the person to surrender weapons temporarily.

Police officials in Madison have not provided a motive in the shooting, which killed Rubi P. Vergara, 14, a freshman whose online obituary said she loved to read and played keyboard in a worship band, and Erin M. West, 42, who lived in a nearby town and was Abundant Life’s substitute teacher coordinator. Six other people were wounded in the attack, which investigators said ended after the assailant fatally shot herself.

Law enforcement officials have been reviewing the shooter’s activities online and said they were aware of versions of a manifesto that was shared on social media. However, they cautioned that they had not been able to verify the authenticity of those documents.

Police officials in Madison said the shooter used a handgun. On Wednesday, they said investigators found a second firearm at the scene that was not fired during the attack. The authorities have not said how the shooter got access to the weapons. Until the California court filing came to light, there had been no sign of a broader plot.

Neighbors said that they had known Natalie, who recently went by Samantha, since she was a little girl, when she was just one of the many neighborhood children who played together.

Cindy Pulvermacher, who lives two doors away from where the shooter lived, said that Natalie’s father, Jeff Rupnow, was often seen walking his daughter home from the elementary school.

“If I thought she had issues, I probably wouldn’t be surprised by what happened,” Ms. Pulvermacher said. “But my thought was, she was just a normal kid.”

Another neighbor, who said she used to babysit Natalie, said that Mr. Rupnow transferred her to Abundant Life this fall at Natalie’s request. The neighbor, who did not want to be named out of concern for her privacy, had last seen Natalie on Halloween, when the girl stopped by for candy.

When the neighbor heard of the shooting, she texted Mr. Rupnow and asked if it was the same school that Natalie attended.

Mr. Rupnow responded that it was. The neighbor followed up asking if his daughter was safe, but never received a reply.