However Steve Flaherty, the superintendent of the Virginia State Police, said while it was reasonable to assume that Cho was the shooter in both the first attack on a dormitory and the second, around two hours later at the university’s engineering department, that link was not yet definitive.
"There's no evidence of any accomplice at either event, but we're exploring the possibility," he said.
Police said Cho was 23 and studying English literature. Authorities said he was a legal resident of the US but further details on his background were harder to find.
"He was a loner, and we're having difficulty finding information about him," Larry Hincker, a spokesman for the university, said.
The shootings are the worst in US history and have been condemned by, among others, George Bush, the US president, and the pope.
Bush was expected to attend a memorial service due to be held at the university later on Tuesday, the White House said.
The state's governor Tim Kaine was flying back to Virginia from Tokyo for the ceremony.
Television images of terrified students and police dragging out bloody victims are likely to renew debate about America's gun laws.
Police said the gunman appeared to have used chains to lock doors and prevent victims from escaping.
Fifteen people were wounded, including those shot and students hurt jumping from windows in a desperate attempt to flee the gunfire.
The first shooting was reported to campus police at about 7:15am (1115 GMT) in West Ambler Johnston Hall, a dormitory housing around 900 students.
Two hours later, dozens of shots were fired a 800m away at Norris Hall, site of the science and engineering school.