WASHINGTON - The Virginia Tech student identified as the assailant in Monday's deadly gun rampage was a South Korean immigrant who had been in the United States since 1992 and who held a green card signifying his status as a legal permanent US resident, federal officials said Tuesday.

Cho Seung-Hui, a 23-year-old English major, was listed with a home address in Centreville, Va., a suburb of Washington, D.C., not far from Dulles International Airport.

Immigration records maintained by the Department of Homeland Security show that Cho was born in South Korea on Jan. 18, 1984 and entered the United States through Detroit on Sept. 2, 1992. He had last renewed his green card on Oct. 27, 2003.

University officials said he lived in a dormitory on the Virginia Tech campus, but could shed no light on a motive for the shooting spree that left 33 dead. "He was a loner, and we're having difficulty finding information about him," said Virginia Tech spokesman Larry Hincker.

Cho's fingerprints were found on two handguns used in the rampage, said two law enforcement officials who spoke on condition of anonymity because the information had not been announced. The serial numbers on the two weapons had been filed off, the officials said.

Ballistics tests by the federal Bureau of Alcohol, Tobacco and Firearms showed that one of the guns was used in both of Monday's separate campus attacks that happened two hours apart.

Cho was found with a backpack containing a receipt for a Glock 9mm pistol that he had bought in March.

As a legal permanent US resident, Cho had the same rights as a citizen for the purposes of buying and possessing firearms. In Virginia, a green card holder must establish that he has been a resident of the state for at least 90 days by providing a valid photo ID plus documentation such as a utility bill or lease.

The state's firearms purchase eligibility test lists 16 questions that all must be answered "no" for the purchase to go forward, including whether the applicant is under indictment for a felony or has been convicted of a felony; has been adjudicated a delinquent as a juvenile; is subject to an outstanding protective or restraining order; is an unlawful user of any controlled substance; or has ever been judged legally incompetent or mentally incapacitated or been involuntarily committed to a mental institution.

Since 1993 it has been illegal for any person not a licensed firearms dealer to purchase more than one handgun within any 30-day period. The state does not maintain registration lists of firearms owners.