Cho prepared in advance for rampage

We're getting a better picture of just how heavily armed Seung-Hui Cho was — a further sign of how much he had done in advance of the shootings to prepare himself for his rampage.

Virginia State Police say they're nearly done with their on-scene investigation at Virginia Tech. But inside the classroom building, investigators say they found a surprising number of handgun magazines, or clips — 17. Some, officials say, were high-capacity magazines that hold 33 rounds. That means, investigators say, that Cho may have fired at least 200 times during his killing spree on Monday.

In the photos Cho sent to NBC, he showed some of his ammunition — hollow-point rounds, purchased, officials say, in the weeks before the shootings. Law enforcement officials say hollow-points are generally considered more lethal.

Joseph Vince, a retired ATF agent, agrees.

"It's not something that you would need for home protection, because what you are trying to do is eliminate an immediate threat," Vince says. "The idea of killing is what this ammunition portrays to me."

Investigators also say Cho practiced shooting at a firing range in Roanoke, about 40 miles from the campus, in mid-March.

As for the video clips Cho sent NBC, with his rambling rants, a Virginia State Police official on Thursday said he's disappointed that NBC News chose to broadcast some of Cho's words.

"Virginia Tech families endured, and indeed, the world has endured, a view of life that few of us should or would ever have to endure," said Virginia State Police Officer Steve Flaherty.

But NBC News says only a small portion of the material was broadcast.

"People asked all week long what was inside the mind of this killer and what was he thinking, what led him to do this," NBC News President Steve Capus said. "When that material landed on our doorstep here, I thought we had an obligation."

A further insight into Cho's background comes from high school classmates in suburban Washington who say he was bullied and laughed at over his Korean accent and shyness. When called on in class, they say, he would hang his head in silence.

Thursday, Virginia Tech officials said they would honor the students killed Monday by giving them college degrees posthumously, to be awarded at commencement in May.