Blacksburg, Va. ? The Internet activities of the Virginia Tech gunman provided more insight Saturday into how he may have plotted for the rampage, with revelations that he bought two ammunition clips on eBay.

Seung-Hui Cho purchased two empty clips about three weeks before the attack in which Cho killed 32 people and himself. The clips were designed for one of the two types of handguns he used.

Cho, 23, also used the account to sell items ranging from Hokies football tickets to horror-themed books, some of which were assigned in one of his classes.

EBay spokesman Hani Durzy said the purchase of the clips from a Web vendor based in Idaho was legal and that the company has cooperated with authorities.

A search warrant affidavit filed Friday stated that investigators wanted to search Cho’s e-mail accounts, including the address Blazers5505hotmail.com.

Durzy confirmed Cho used the same blazers5505 handle on eBay.

Virginia State Police spokeswoman Corinne Geller said investigators are “aware of the eBay activity that mirrors” the Hotmail account.

The eBay account demonstrates the prime role computer forensics and other digital information have played in the investigation. Authorities are examining the personal computers found in Cho’s dorm room and seeking his cell-phone records.

One question they hope to answer is whether Cho had any e-mail contact with Emily Hilscher, one of the first two victims. Investigators plan to search her Virginia Tech e-mail account.

Experts say that when the subject of an investigation is a loner like Cho, his computers and cell phone can be a rich source of information. Authorities say Cho had a history of sending menacing text messages and other communications – written and electronic.

On March 22, Cho bought two 10-round magazines for the Walther P22.

A day later, he made a purchase from a vendor named “oneclickshooting,” which sells gun accessories and other items. Details on the purchase were unclear, and the seller could not be reached for comment.