Law enforcement sources told CBS News that Cho fired between 175 and 225 shots. The majority of that was from the 9 mm Glock. There were between 15 and 17 cartridges of ammo, some of them of extended capacity.
"Once the shooting starts, there are always more shots fired than people think. That's kind of the nature of the beast," one law enforcement source said.
Cho had walked into the Roanoke Firearms store five weeks before the shooting, put down a credit card and walked out with the Glock 19 automatic and a box of ammunition. The card was docked $571.
"It was a very unremarkable sale," said John Markell, the store's owner. "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."
Cho was from South Korea, but he held a green card, meaning he was a legal, permanent resident of the United States, according to federal officials. That made him eligible to buy a handgun unless he had been convicted of a felony.
The 22-caliber Walther semi-automatic pistol used by Cho in the killings was purchased on the Internet from a Green Bay, Wisconsin based website The Gun Source, CBS News has learned.
Cho bought the pistol with a credit card for $267 on Feb. 2 and picked it up one week later at a pawnshop near the Virginia Tech campus in Blacksburg, Va.
In an email exchange with the online vendor, Cho wanted assurance he was getting the latest model.
"Is Walther P22 product 10632 second generation? What year was the assembly date?" he asked.
"All our firearms are the latest generation," the store replied. (See the complete email exchange on the CBS News Primary Source Blog
Eric Thompson, president of TGSCOM, which owns 50 websites that sell guns, confirmed that The Gun source sold Cho the Walther P22.
"As a father of three, I was obviously heart-broken when I found out," Thompson said in an interview with CBS affiliate WFRV. "I feel so terrible."
Under federal law, only federally-licensed firearms dealers may ship handguns across state lines and then only to other licensed dealers.
Thompson said his company is cooperating with law enforcement agencies investigating the nation's worst ever domestic shooting incident.
"Our thoughts and prayers are with the families of the victims," Thompson said, adding that his websites would be adding links to the Hokie Spirit Memorial Fund established by Virginia Tech.