Jared L. Loughner

Tucson (Arizona), Jan. 10: In a community college classroom here last June, on the first day of the term, the instructor in Jared L. Loughner’s basic algebra class, Ben McGahee, posed what he thought was a simple arithmetic question to his students. He was not prepared for the explosive response.

“How can you deny math instead of accepting it?” Loughner asked, after blurting out a random number, according to McGahee.

The teacher, for one, was disturbed enough by the experience to complain to school authorities, who as early as last June were apparently concerned enough themselves to have a campus officer visit the classroom.

And what McGahee described as a pattern of behaviour by Loughner, marked by hysterical laughter, bizarre non sequiturs and aggressive outbursts, only continued.

“I was getting concerned about the safety of the students and the school,” said McGahee, who took to glancing out of the corner of his eye when he was writing on the board for fear that Loughner might do something. “I was afraid he was going to pull out a weapon.”

A student in the class, Lynda Sorenson, 52, wrote an email to a friend expressing her concerns. “We do have one student in the class who was disruptive today, I’m not certain yet if he was on drugs (as one person surmised) or disturbed. He scares me a bit,” Sorenson wrote in an email in June that was forwarded yesterday to The New York Times.

“The teacher tried to throw him out and he refused to go, so I talked to the teacher afterward. Hopefully he will be out of class very soon, and not come back with an automatic weapon.”

Loughner’s behaviour grew so troubling that he was told he could no longer attend the school, and he appeared, given his various Internet postings, to find a sense of community in some of the more paranoid corners of the Internet.

Loughner seems at some point to have crossed a border. From being a young man whom acquaintances described as odd, he became the sole suspect in the shooting of Representative Gabrielle Giffords, a Democrat from Arizona’s Eighth District.

Robert S. Mueller III, the FBI director, who has taken charge of the investigation here, said at a news conference that possible links to extremist groups would be a continued focus.

“The ubiquitous nature of the Internet means that not only threats but also hate speech and other inciteful speech is much more readily available to individuals than quite clearly it was 8 or 10 or 15 years ago,” Mueller said. “That absolutely presents a challenge for us.”

The words echoed comments by Pima county Sheriff Clarence W. Dupnik, who said on Saturday at a news conference that “unbalanced people” could be affected by the vitriol, anger and hatred of anti-government rhetoric.