A 20-year-old man from Carlsbad, California, has been detained for allegedly conspiring to carry out a mass shooting at a government building in coordination with a teenage girl who opened fire at a Christian school in Wisconsin earlier this week.

20-year-old Alexander Paffendorf from Carlsbad California.
Detained by FBI.
Authorities say he plotted with Natalie “Samantha” Rupnow to commit an additional mass shooting at a government building. https://t.co/cpnbulvvuU pic.twitter.com/IN53U2RZsK

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The alleged plan was revealed in court documents and law enforcement interviews.

Alexander Paffendorf reportedly exchanged messages with Natalie “Samantha” Rupnow, a 15-year-old student at Abundant Life Christian School in Madison, Wisconsin.

According to a gun violence restraining order obtained by CBS 8, the two discussed parallel attacks—Rupnow targeting her school while Paffendorf allegedly planned to strike a government building.

“During an FBI interview, Paffendorf admitted to the FBI agents that he told Rupnow that he would arm himself with explosives and a gun and that he would target a government building,” stated the emergency restraining order filed by the Carlsbad Police Department.

Rupnow tragically carried out the shooting at her school on Monday, killing two individuals: Erin West, a 42-year-old substitute teacher, and Rubi Vergara, a 14-year-old freshman.

Rupnow also wounded five other students and another teacher before taking her own life. Two of the injured students remain in critical condition.

The restraining order does not specify which government building Paffendorf allegedly intended to target or provide extensive details about his conversations with Rupnow.

The San Diego Superior Court approved the emergency order under California’s red flag gun law on Tuesday night, CBS 8 reported.

The order requires Paffendorf to surrender all firearms and ammunition to law enforcement within 48 hours.

Shortly after the order was issued, law enforcement responded to Paffendorf’s residence with a significant presence.

“They had their full guns out all over the street,” neighbor Alex Gallegos told CBS 8. “There were cop cars. I’d say about 15 cops here.”

According to Gallegos, officers were seen removing a large gun box from the home during the operation.

Authorities are working to uncover more details about the motivations behind Rupnow’s actions and any further plans discussed between her and Paffendorf.

The communication between the two could provide key insights into the high school freshman’s decision to carry out the deadly attack at her school.

The attack at Abundant Life Christian School has left the Madison community grieving. In addition to the two fatalities, five students and one teacher sustained injuries during the shooting.

Local officials have confirmed that two of the injured students remain hospitalized in critical condition.

Law enforcement and community members continue to search for answers as investigations proceed.