The message, which was posted between the two killing sprees Monday and received by NBC on Tuesday, was full of anger and hate and cried out unspecified wrongs done to the English major in a diatribe laced with profanity.

"I didn't have to do this. I could have left. I could have fled. But no, I will no longer run. It's not for me. For my children, for my brothers and sisters that you ****, I did it for them," Cho says on one of the videos, according to NBC.

Into the mind of the Virginia Tech shooter

He also claimed that he was being forced into the act and blamed others for the killings. "You had a hundred billion chances and ways to have avoided today," Cho said. "But you decided to spill my blood. You forced me into a corner and gave me only one option. The decision was yours. Now you have blood on your hands that will never wash off," he ranted.

"When the time came, I did it. I had to do it," he wrote and also railed against the rich and unspecified enemies. Officials said the package might explain what Cho was doing during the two hours between the first shooting and the second one in which most of the victims were killed.

The package bore a US Postal Service stamp recording that it had been received a Virginia post office at 9:01 am Monday, about one hour and 45 minutes after the first shooting and shortly before he entered the Norris Hall for the second spree.

Images: A massacre at Virginia Tech

NBC News President Steve Capus said the network received the package in Tuesday afternoon's mail delivery, but it was not opened until Wednesday morning.

The letter carrier noticed that it bore a return address from Blacksburg and alerted NBC security officers. The material, including an 1,800-word manifesto-like statement is "hard to follow... disturbing, very disturbing," Capus said in an interview late on Wednesday afternoon.

Among the materials, NBC said, was a DVD with 27 video files, totaling about 10 minutes, showing Cho talking directly to the camera. He does not name anyone specifically, but he mentions "hedonism" and Christianity, and he talks at length about his hatred of the wealthy.

'This is the saddest day in our lives'

"You have vandalised my heart, raped my soul and torched my conscience. You thought it was one pathetic boy's life you were extinguishing. Thanks to you, I die like Jesus Christ, to inspire generations of the weak and the defenseless people."

"Do you know what it feels like to be humiliated and be impaled upon on a cross? And left to bleed to death for your amusement? You have never felt a single ounce of pain your whole life. Did you want to inject as much misery in our lives as you can just because you can?"

The material did not include any images of the shootings Monday, but it does contain vague references. And it mentioned "martyrs like Eric and Dylan" -- apparently a reference to Eric Harris and Dylan Klebold, the teenagers who killed 12 students and a teacher at Columbine High School in Littleton, Colorado eight years ago this coming Friday.

The disturbed English student also claimed he was a victim facing persecution. "Do you know what it feels to be spit on your face and to have trash shoved down your throat? Do you know what it feels like to dig your own grave?

"Do you know what it feels like to have throat slashed from ear to ear? Do you know what it feels like to be torched alive?" Cho also ranted against the rich, claiming they always wanted more than what they had.

"You had everything you wanted. Your Mercedes wasn't enough, you brats. Your golden necklaces weren't enough, you snobs. Your trust fund wasn't enough. Your vodka and Cognac weren't enough. All your debaucheries weren't enough. Those weren't enough to fulfill your hedonistic needs. You had everything."

The production of the videos is uneven, with Cho's voice so soft that at times it is hard to understand him. But they indicated that Cho had worked on the package for some time, because he not only "took the time to record the videos, but he also broke them down into snippets," Capus said.

There was no indication why Cho chose NBC News to receive the package, which was immediately turned over to FBI agents. Capus said NBC News was cooperating with Virginia State Police and the FBI, which is assisting the state police.

At times, Cho can be seen leaning forward to turn off the camera, suggesting that he shot the videos himself. The package also included 43 photographs. Cho looks like a normal, smiling college student in only the first two. In the rest, he presents a stern face. In 11, he aims handguns at the camera that are "consistent with what we've heard about the guns in this incident," Capus said. Cho's name was not on the package; instead, the return address said it came from "Ishmael".

Investigators said Cho's body was found Monday with the words "Ismael Ax" scrawled on his arm. Capus said the network would have received the package earlier had the Korean not written the wrong address.

"We probably would have received the mail earlier had it not been that he had the wrong address and ZIP code," he said.