(Carlsbad, CA) -- A 20-year-old man from Carlsbad, California has been detained by authorities on suspicion of plotting a mass shooting in conjunction with Madison's school shooter. A gun violence restraining order claims the man was in contact with 15-year-old Natalie Rupnow and was coordinating an attack at a government building in the Carlsbad area. The restraining order allows police to seize weapons from the California man. He allegedly admitted to FBI agents that he told Rupnow he would arm himself with explosives and a gun and would target a government building. On Monday, Rupnow shot a teacher and a student to death at Abundant Life Christian School in Madison, Wisconsin. She also wounded six other victims before dying of a self-inflicted gunshot wound.