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, whose 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."

On Tuesday afternoon, thousands of people gathered in the basketball arena for a memorial service for the victims, with an overflow crowd of thousands watching on a jumbo TV screen in the football stadium. President Bush and the first lady attended.

"As you draw closer to your families in the coming days, I ask you to reach out to those who ache for sons and daughters who are never coming home," Bush said.

Virginia Tech President Charles Steger received a 30-second standing ovation, despite the criticism of the school administration.

With classes canceled for the rest of the week, many students left town in a hurry, lugging pillows, sleeping bags and backpacks down the sidewalks.

Jessie Ferguson, 19, a freshman from Arlington, headed for her car with tears streaming down her cheeks.

"I'm still kind of shaky," she said. "I had to pump myself up just to kind of come out of the building. I was going to come out, but it took a little bit of 'OK, it's going to be all right. There's lots of cops around."'

She added: "I just don't want to be on campus."