At least one of those killed in the rampage, Reema Samaha, graduated from Westfield High in 2006. But there was no immediate word from authorities on whether Cho knew the young woman and singled her out.

"He was very quiet, always by himself," neighbor Abdul Shash said. Shash said Cho spent a lot of his free time playing basketball and would not respond if someone greeted him.

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Some classmates said that on the first day of a British literature class last year, the 30 or so students went around and introduced themselves. When it was Cho's turn, he didn't speak.

On the sign-in sheet where everyone else had written their names, Cho had written a question mark. "Is your name, `Question mark?'" classmate Julie Poole recalled the professor asking. The young man offered little response.

Cho spent much of that class sitting in the back of the room, wearing a hat and seldom participating. In a small department, Cho distinguished himself for being anonymous. "He didn't reach out to anyone. He never talked," Poole said.

"We just really knew him as the question mark kid," Poole said.

One law enforcement official said Cho's backpack contained a receipt for a March purchase of a Glock 9 mm pistol. Cho held a green card, meaning he was a legal, permanent resident. That meant he was eligible to buy a handgun unless he had been convicted of a felony.

Roanoke Firearms owner John Markell said his shop sold the Glock and a box of practice ammo to Cho 36 days ago for $571.

"He was a nice, clean-cut college kid. We won't sell a gun if we have any idea at all that a purchase is suspicious," Markell said.

Investigators stopped short of saying Cho carried out both attacks. But State Police ballistics tests showed one gun was used in both.

And two law enforcement officials, speaking on condition of anonymity because the information had not been announced, said Cho's fingerprints were on both guns. Their serial numbers had been filed off.

Gov. Tim Kaine said he will appoint a panel at the university's request to review authorities' handling of the disaster. Parents and students bitterly complained that the university should have locked down the campus immediately after the first burst of gunfire and did not do enough to warn people.

Kaine warned against making snap judgments and said he had "nothing but loathing" for those who take the tragedy and "make it their political hobby horse to ride."

"I'm satisfied that the university did everything they felt they needed to do with the heat on the table," Kaine told CBS' "The Early Show" on Wednesday. "Nobody has this in the playbook, there's no manual on this."

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