The killer is revealed.

The man behind these gruesome murders has been identified as 23-year, Cho Seung-Hui. Seung-Hui is a student of Virginia Tech, an English major. He also left a very long letter, several pages long, and it is described to be "disturbing" and in the letter it says "You caused me to do this". The police are saying that after he killed the two people in the dorm he returned to his dorm room, re-armed, left the note and then went to a classroom building on the other side of campus.

Cho, born in South Korea, was a legal resident alien of the United States. He was in his senior year.

Sources tell ABC News Cho bought his first gun, a Glock 9 millimeter handgun, on March 13; they say he bought his second weapon, a .22 caliber pistol, within the last week. The serial numbers on both guns had been filed off, they said.

Authorities found the receipt for the 9 millimeter handgun in Cho's backpack. They say the bag also contained two knives and additional ammunition for the two guns.

Cho's identity has been confirmed by matching fingerprints on the guns used in the rampage with his immigration records.

"Lab results confirm that one of the two weapons seized in Norris Hall was used in both shootings," Virginia Tech Police Chief Wendell Flinchum said at a press conference Tuesday morning.

At this time, police are not looking for a second shooter, though they did not rule out the possibility that Cho could have had an accomplice.

"He was a loner, and we're having difficulty finding information about him," said Virginia Tech spokesman Larry Hincker.

It also was confirmed that Cho Sueng-Hui did commit suicide before police were able to break the lock of the door and reach him. Police said he shot himself in the face, "part of his face was missing when his body was found".