Seung Hui Cho

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Seung Hui Cho, a permanent resident of the United States, a Korean national and a Virginia Tech student has been identified as the gunman in the shootings that left 33 people dead on the Virginia Tech campus Monday, ABC News has learned.

The student left a "disturbing note" before killing two people in a dorm room, returning to his own room to re-arm and entering a classroom building on the other side of campus to continue his rampage, sources said.

Cho's identitiy has been confirmed with a positive fingerprint match on the guns used in the rampage and with immigration materials. It is believed that he was the shooter in both incidents yesterday. Sources say Cho was carrying a backpack that contained receipts for a March purchase of a Glock 9 mm pistol, sources said. Witnesses had also told authorities that the shooter was carrying a backpack. Sections of chain similar to those used to lock the main doors at Norris Hall, the site of the second shooting that left 31 dead, were found inside a Virginia Tech dormitory, sources confirmed to ABC News.

In all, the massacre at Virginia Tech left 33 people dead — including Cho himself — in the worst shooting in moder American history.

President Charles Steger told "Good Morning America's" Diane Sawyer that police were still investigating the possibility of a second shooter, and said authorities had already interviewed one "person of interest." "There may be others," said Steger, who will join the Virginia Tech chief of police at a press conference Tuesday morning. "We just don't know." Steger also said that authorities hoped to have ballistics evidence to release that would confirm a connection between the two shootings.

In a press conference Monday night, the university president, who continues to defend the way the school responded the dormitory shooting that began the day of campus bloodshed, gave a detailed timeline of the morning's tragic events. He said a 911 call reporting a shooting at a dormitory was made at approximately 7:15 a.m. While police were trying to assess what they first believed was a domestic dispute, they received a second 911 call, nearly two and a half hours later, that reported shootings on the opposite side of campus. According to the Virginia Tech Police Chief Wendell Flinchum, officials have not definitively linked the two shootings.

Two guns were recovered, a 9 mm pistol and a .22-caliber pistol.

Flinchum said they have ruled out the possibility of a murder-suicide in the shooting at West Ambler Johnston Hall. Ryan "Stack" Clark, a member of the school's marching band, the Marching Virginians, and a student resident assistant, was killed there by a shot in the neck. The second victim in the dorm shooting was a female.

Last night, investigators also had a preliminary identification of the shooter involved in the Norris Hall rampage.

When asked to describe the scene at Norris Hall, where the second shooting took place, Flinchum called it "one of the worst things I've seen in my life."