Cho Seung-Hui, a child immigrant from South Korea who grew up in the Washington suburbs, was portrayed by fellow students and teachers as an insecure loner who ate by himself night after night, watched TV wrestling shows alone and, when spoken to, had little to say.

Well-known poet Nikki Giovanni, who taught him creative writing, observed him in the class with dark sunglasses and a ball cap jammed down over this face. He turned in assignments she found disturbing. Sometimes he snapped unwanted cell-phone photos of classmates. Students stopped showing up for class, telling her, "The guy's really creepy." At one point she had security guards stationed nearby.

Authorities continued yesterday to assemble the pieces of Cho's life on the campus in the Blue Ridge Mountains, but it was still unclear what motivated him. No link has been disclosed between Cho and any of the victims.

"We're still following all these leads. There's a myriad of leads," state Police Superintendent Col. Steven Flaherty said. "There is a lot of evidence, and it's slow moving."

Cho did not appear to have any friends or a girlfriend, said Joseph Aust, one of five students who shared his dormitory suite. He wore a standard uniform — blue jeans, T-shirt and maroon Virginia Tech hat, and kept only text books and a laptop computer. His one known passion was downloading music.

He hung no pictures, posters or decorations on his walls, and avoided conversations with roommates and other students.

"He would just give one-word answers," Aust said.

But in recent weeks, Cho's habits had begun to change. He ventured out at night to the campus gym, lifting weights, and he trimmed his hair into a military-style buzz cut.

BOMB THREATS

Police said they have found "considerable writings" in Cho's room, including rants about wealthy kids and debauchery.

Yet in contrast to that image of a lost and angry soul on a campus of 26,000 students, Cho's last acts were one of calm determination. He sent a series of bomb threats to school officials, authorities believe. He chained the doors on Norris Hall and brought along enough ammunition to kill 50. Police also said he tried to shave the serial numbers off his new Walther P22 and 9mm Glock, both heavy handguns. And he was careful enough not to carry any identification.

A law enforcement source said Cho bought the .22-caliber Walther at JND Pawnbrokers in Blacksburg in February, and he bought the Glock Model 19, which retails for more than $500, on March 12 at the Roanoke Firearms store in Roanoke, Va.

Both were bought legally, said the federal official, and both licensees did everything they were required to do, including conducting appropriate background checks on Cho before selling him the handguns.

Campus and state police said ballistics tests showed that one of the two handguns fired by Cho in Norris Hall was also used to kill the two students in the dorm two hours earlier.

Born on Jan. 18, 1984, Cho emigrated to the United States from South Korea in September 1992, arriving first in Detroit, according to the Korean Embassy in Washington. He renewed his green-card status in October 2003 but apparently retained his South Korean citizenship.

'STARING AT NOTHING'

His parents moved to Centreville, Va., about 20 miles west of the capital and reportedly ran a dry-cleaning concern in the fast-growing suburb that has drawn many South Korean immigrants. Cho attended Westfield High School and was a member of the science club, school officials said. He graduated in 2003.

His roommates said they never noticed any weapons or unusual items — except Monday morning, after Cho left for class, when Aust saw a screwdriver on his roommate's desk.

Other times, Aust found Cho sitting silently in a desk chair, apparently oblivious. "He'd just kind of be staring at his desk, just staring at nothing," he said. "I would pass it off like he was just weird."

Several students and professors who had seen Cho's poetry, plays and fiction writing from 2005 described it as filled with graphic violence.

Lucinda Roy, chairwoman of the English department, worried about his stability and urged him to seek counseling at the school. He turned down her suggestion.

Giovanni, the former creative writing instructor, said she took some of Cho's writing to Roy and told her that she no longer could teach him.

"I couldn't allow him to destroy my class," she said.

Roy agreed to teach Cho in private, Giovanni said.

Two of Cho's plays have been posted on the Web. In one, three students trade vicious, scatological banter about killing their teacher. In the other, a boy accuses his stepfather, Richard McBeef, of killing his father. "I hate him," he says. "Must kill Dick. Must kill Dick. Dick must die."

The play ends wordlessly, with stage directions: "(Out of sheer desecrated hurt and anger, Richard lifts his large arms and swings a deadly blow at the thirteen year old boy.)"

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