BLACKSBURG, Virginia (CNN) -- Cho Seung-Hui said Monday's massacre on the Virginia Tech campus could have been avoided and said "you forced me into a corner," in a videotaped message he mailed to NBC News.
NBC News reported that Cho mailed the package at 9:01 a.m. Monday -- during the two hours between the shootings at the West Ambler Johnston Hall dormitory and the shootings at Norris Hall.
"You had a hundred billion chances and ways to have avoided today," Cho said in one of the videos that aired Wednesday night on NBC. "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." (Watch Cho's menacing last messages )
In another video broadcast on NBC, Cho told the camera "When the time came I did it, I had to."
Cho spoke about the shootings in the past tense, but it is unclear when the video messages were recorded.
MSNBC.com reported that Cho also discussed "martyrs like Eric and Dylan" apparently referring to Columbine High School gunmen Eric Harris and Dylan Klebold, who killed 13 people and themselves on April 20, 1999.
Cho railed against the wealthy and other unnamed enemies in the angry messages.
"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," MSNBC.com quoted Cho as saying.
The package included an 1,800 word statement described as "a manifesto" and 27 QuickTime videos showing Cho Seung-Hui talking to the camera and discussing religion and his hatred of the wealthy, MSNBC.com reported. (Interactive: Cho's manifesto)
It also included several photographs of Cho posing and pointing handguns at the camera.
At least one photograph showed Cho pointing a pistol at his head. Another showed Cho holding a knife to his throat.
The package was sent by overnight mail, but did not arrive until Wednesday because the address and Zip code were wrong.
"This may be a very new critical component of this investigation," State Police Col. Steve Flaherty said.
When the network received the package, it immediately notified authorities and the original documents were sent to the FBI for analysis, Flaherty said.
CNN also learned Wednesday that in 2005 Cho was declared mentally ill by a Virginia special justice, who declared he was "an imminent danger" to himself, a court document states.
A temporary detention order from General District Court in the commonwealth of Virginia said Cho "presents an imminent danger to himself as a result of mental illness."
A box indicating that the subject "Presents an imminent danger to others as a result of mental illness" was not checked.
In another part of the form, Cho was described as "mentally ill and in need of hospitalization, and presents an imminent danger to self or others as a result of mental illness, or is so seriously mentally ill as to be substantially unable to care for self, and is incapable of volunteering or unwilling to volunteer for treatment."
A handwritten section of the form describes Cho. "Affect is flat and mood is depressed," said the order, which was signed December 14 by Special Justice Paul M. Barnett. "He denies suicidal ideation. He does not acknowledge symptoms of a thought disorder. His insight and judgment are normal."
Student complaints
Police first investigated Cho in November 2005 after a student complained about him calling her and contacting her in person, university police Chief Wendell Flinchum said.(Watch how police learned of Cho's troubles )
Cho was sent to the university's Office of Judicial Affairs, which handled the complaint, the outcome of which is confidential, university officials said.
"The student declined to press charges and referred to Cho's contact with her as annoying," Flinchum said of the November investigation.
Police investigated him again the next month when a female student complained about instant messages Cho sent her, Flinchum said.
"Again, no threat was made against that student. However, she made a complaint to the Virginia Tech Police Department and asked that Cho have no further contact with her," the chief said.
After police spoke to Cho, they received a call from a student concerned that he might be suicidal.
Officers spoke to Cho "at length" then asked him to see a counselor. He agreed to be evaluated by Access Services, an independent mental health facility in Blacksburg, the chief said.
"A temporary detention order was obtained and Cho was taken to a mental health facility" on December 13, 2005, he said.
A student asking to be identified only as Andy said he was the one who told police that Cho was suicidal. Police "took [Cho] away to the counseling center for a night or two," said the student, who used to room with Cho. (Watch Cho's roommates describe his 'crazy' behavior )
Authorities said they received no more complaints about Cho before the shootings, Flinchum said.
The university and its police continue to defend themselves against students' complaints that they weren't adequately warned about Cho -- even after two people were killed in a dormitory early Monday morning. (Watch how large universities protect students )
Though police have linked a gun used in Norris Hall -- where 31 people, including Cho, died -- they have yet to say he is officially accused of the first shootings. (Learn more about those killed in the rampage)
Professor recalls 'mean streak'
As tales of Cho's worrisome behavior continued to surface Wednesday, a renowned poet and author who taught the 23-year-old gunman called the notion that he was troubled "crap" and said he was "mean."
Nikki Giovanni said she immediately suspected Cho when she got word of the shootings. (Watch Giovanni declare at a Tuesday convocation, 'We are Virginia Tech' )
"I knew when it happened that that's probably who it was," Giovanni said, referring to her former pupil. "I would have been shocked if it wasn't."
Cho's poetry was so intimidating -- and his behavior so menacing -- that Giovanni had him removed from her class in the fall of 2005, she said. Giovanni said the final straw came when two of her students quit attending her poetry sessions because of Cho.
"I was trying to find out, what am I doing wrong here?" Giovanni recalled thinking, but the students later explained, "He's taking photographs of us. We don't know what he's doing." (Classmates called Cho 'question mark kid')
Giovanni went to the department's then-chairwoman, Lucinda Roy, and told her, "I was willing to resign before I was going to continue with him." Roy took Cho out of Giovanni's class.
"I know we're talking about a troubled youngster and crap like that, but troubled youngsters get drunk and jump off buildings; troubled youngsters drink and drive," Giovanni said. "I've taught troubled youngsters. I've taught crazy people. It was the meanness that bothered me. It was a really mean streak." (Watch how the cause of Cho's behavior could have been physical )
Roy, who taught Cho one-on-one after removing him from Giovanni's class, recalled Cho exhibiting a palpable anger and secretly taking photographs of other students while holding the camera under his desk. (Watch the professor tell how her student frightened her )
His writings were so disturbing, she said, that she went to the police and university administrators for help.
"The threats seemed to be underneath the surface," she said. "They were not explicit and that was the difficulty the police had."
Ian MacFarlane, who had class with Cho, said two plays written by Cho were so "twisted" that McFarlane and other students openly pondered "whether he could be a school shooter." (Read MacFarlane's blog and the two plays)
University stands by handling of shooting
Though two professors, Cho's former roommates and a classmate and police all recall Cho behaving in a disturbing manner, officials said there was nothing criminal about his demeanor.
The gun shop owner who sold him the Glock 9 mm, one of the guns used at Norris Hall, said Cho easily passed a background check last month before buying the weapon. (Watch dealer recount selling weapon to Cho )
Asked about Roy's concerns that Cho was writing troubling plays and poems in his classes, Flinchum said no official report was filed.
"These course assignments were for a creative writing course and the students were encouraged to be imaginative and artistic," the chief said. "The writings did not express any threatening intentions or allude to criminal activity. No criminal violation had taken place."
Flinchum's remarks were the latest in the university's defense, not only of its handling of situations that arose before the shootings, but also of how it handled situations in the immediate aftermath of the shooting at West Ambler Johnston dorm.
The recurring question: Why weren't students warned or the campus locked down before Cho was able to walk into Norris Hall more than two hours later and exact the deadliest mass shooting in U.S. history? (Watch how Virginia Tech students will never forget Monday's massacre )
Flinchum said Wednesday that details gleaned from the investigation at the dorm led to a decision among university officials and police that the campus did not need to be locked down.
"There are a lot of details we were providing to the administration and a decision was made based on that information," the chief said.
University President Charles Steger has said police believed the incident was "a domestic fight, perhaps a murder-suicide" that was contained to one dorm room.
Police cordoned off the 895-student dorm and all residents were told about the shooting as police looked for witnesses, Steger said.
"I don't think anyone could have predicted that another event was going to take place two hours later," Steger said.
Authorities are still investigating whether Cho had any accomplices in planning or executing Monday's rampage.