The alleged co-conspirator of a Wisconsin school shooter has been called “very scary” and “calm” by current and former neighbors.

The alleged co-conspirator in the Wisconsin school shooting was described as sinisterly “scary” and “quiet” by his current and former California neighbors, according to reports.

An unidentified ex-neighbor from San Diego described Alexander Paffendorf, 20, as “very scary,” describing how she “never heard him say a word” despite living next door to him and his parents for six years, TMZ reported.

“He looks like someone who would shoot up a place,” she said, adding that neighbors had theories about him before he was accused of plotting a coordinated attack with Natalie “Samantha ” Rupnow, who opened fire at Abundant Life Christian School in Madison on April 17. Monday, killing two people and injuring six.

Paffendorf “always wore a hood” and “did not make eye contact,” according to the neighbor.

She mentioned that he would follow closely behind her as she walked down the stairs and that he had once stood in front of her window, even though he hadn’t said a single word. When she confronted Paffendorf’s parents about him hiding outside her window, they blew her away.

“He was very disconnected from his own world,” she said.

Current neighbors also described Paffendorf as quiet and lonely.

“I’ve only seen him a few times,” the neighbor said. “He’s really quiet, I just saw him walking to his car and back, he said hello, that’s all,” Carlsbad resident Alex Gallegos told NBC Philadelphia.

Authorities revealed Tuesday evening that Rupnow, 15, had been in contact with Paffendorf before the massacre.

Paffendorf allegedly planned a mass shooting at a government building in a parallel, coordinated attack with Rupnow, who killed substitute teacher Erin West and freshman Rubi Vergara before turning the gun on herself- even Monday.

He exchanged messages with Rupnow about targeting a local government building while she was shooting at the school, according to a gun violence restraining order obtained by CBS 8.

“During an interview with the FBI, Paffendorf admitted to FBI agents that he told Rupnow he would arm himself with explosives and a gun and target a government building.” , the Carlsbad Police Department’s two-page emergency restraining order says.

The civil order does not specify which building he allegedly planned to strike or the details of his conversations with Rupnow.

A San Diego Superior Court judge approved the order under California’s gun law Tuesday evening, according to the local California station.

The order required Paffendorf to turn over all his weapons and ammunition to police within 48 hours.

Paffendorf has not been charged with a crime, but a court hearing on the restraining order is scheduled for Jan. 3.

Four days after the school shooting, investigators still have not revealed a motive.