Instead, it took administrators more than two hours to get a strongly worded e-mail out to the students and staff. The shooter had time to leave the dorm, mail a letter, and then return to the classroom building where he chained the doors shut and killed 31 more people, including himself.
The report also faults university officials for failing to identify Seung-Hui Cho, two years ago, as an emerging danger, reports CBS News correspondent Bob Orr.
Professors complained of his violent writings, female students accused him of stalking, and his roommates reported suicide threats.
But the information was not widely shared, adds Orr.
Gov. Timothy M. Kaine formally accepted the report Thursday. "It is comprehensive and thorough, objective and in many cases hard-hitting, and it is fair," he said.
But one victim's mother urged Kaine to "show some leadership" and fire the university's president and campus police chief for their lack of action during the April 16 attack. Others demanded accountability for errors that were made.
Kaine, however, told The Associated Press that the school's officials had suffered enough without losing their jobs.
"This is not something where the university officials, faculty, administrators have just been very blithe," Kaine said Thursday. "There has been deep grieving about this, and it's torn the campus up."
"I want to fix this problem so I can reduce the chance of anything like this ever happening again," he said. "If I thought firings would be the way to do that, then that would be what I would focus on."
The report also revealed that victims' relatives were not well cared for in the days after the shootings, adds Orr.
The eight-member panel, appointed by Kaine, spent four months investigating the worst mass shooting in modern U.S. history.
"Warning the students, faculty and staff might have made a difference," it wrote in a report released Wednesday night. "So the earlier and clearer the warning, the more chance an individual had of surviving."
The first victims were shot shortly after 7 a.m. It wasn't until 9:26 a.m. that the school sent an e-mail to students and faculty warning: "Shooting on campus. The university community is urged to be cautious and are asked to contact Virginia Tech Police if you observe anything suspicious or with information on the case." Cho opened fire inside Norris Hall about 20 minutes later.
The panel's chairman, Gerald Massengill, told the AP on Thursday: "The alert should have been issued and classes should have been closed. If those students had been given a heads-up, then they could maybe have made some decisions that they didn't have an opportunity to make."