"He has made the world weep. We are living a nightmare," said a statement issued by Cho's sister, Sun-Kyung Cho, on the family's behalf. It was the Chos' first public comment since the 23-year-old student killed 32 people and committed suicide Monday.
The family reached out to Raleigh, N.C., lawyer Wade Smith, who provided the statement to the AP. Smith said the family would not answer any questions.
"Our family is so very sorry for my brother's unspeakable actions. It is a terrible tragedy for all of us," said Sun-Kyung Cho, who works as a contractor for a State Department office that oversees American aid for Iraq.
"We pray for their families and loved ones who are experiencing so much excruciating grief. And we pray for those who were injured and for those whose lives are changed forever because of what they witnessed and experienced," she said. "Each of these people had so much love, talent and gifts to offer, and their lives were cut short by a horrible and senseless act."
The family's whereabouts are unclear. But authorities said they are under law enforcement protection.
"We are humbled by this darkness. We feel hopeless, helpless and lost. This is someone that I grew up with and loved. Now I feel like I didn't know this person," she said.
"We have always been a close, peaceful and loving family. My brother was quiet and reserved, yet struggled to fit in. We never could have envisioned that he was capable of so much violence."
She said her family will cooperate fully with investigators and "do whatever we can to help authorities understand why these senseless acts happened. We have many unanswered questions as well."
The statement was issued during a statewide day of mourning for the victims of the worst massacre in U.S. history.
Earlier, shock gave way to grief as silence fell across the Virginia Tech campus at noon Friday and bells tolled in churches nationwide in memory of the 32 victims.
Hundreds of somber students and area residents, most wearing the school's maroon and orange, stood with heads bowed at a memorial on the Drill field in front of Norris Hall, where most of the victims in Monday's massacre died. Along with the bouquets and candles was a yellow sign covered in maroon and orange handprints, bearing the words "Never forgotten."
"It's good to feel the love of people around you," said Alice Lo, an alumna and friend of Jocelyne Couture-Nowak, a French instructor killed in the rampage. "With this evil, there is still goodness."
The mourners gathered in front of simple stone memorials, each adorned with a basket of tulips and an American flag. There were 33 stones — one for each victim and Cho Seung-Hui, the 23-year-old gunman who took their lives.
"His family is suffering just as much as the other families," said Elizabeth Lineberry of Hillsville, who will be a freshman at Tech in the fall.
Devon Shields, a 26-year-old graduate student, stood just outside the ring of stones.
"I almost feel guilty for not being here when it happened," said Shields, who was student-teaching when the shots rang out Monday. "I came here because I just had to connect with it in some way."
Other students returned to daily activities, refusing to let one madman's actions define their lives or the university, reports CBS News correspondent Sharyn Alfonsi. Virginia Tech baseball players, for example, went back to the field.
"We gotta do this," said Tech baseball player Nate Parks. "You can't let somebody who does something like this win."
As experts pored over Cho's videotaped rant and his twisted writings, Gov. Timothy Kaine declared Friday a statewide day of mourning for the victims, and parents urged everyone to focus on the young people cut down in the attack, not the killer.
"We want the world to know and celebrate our children's lives, and we believe that's the central element that brings hope in the midst of great tragedy," said Peter Read, who lost his 19-year-old daughter,. "These kids were the best that their generation has to offer."
Churches around the country, from California to the National Cathedral in Washington, planned vigils and prayer services.
"It's a whole family," said Jan Meehan-Tardiff of Blacksburg, a nurse who has four family members with degrees from Virginia Tech. Around Blacksburg, "you either work at Tech, serve Tech in business or go to Tech."
President Bush wore an orange and maroon tie in a show of support. The White House said he also asked top officials at the Justice, Health and Human Services and Education Departments to travel the country, talk to educators, mental health experts and others, and compile a report on how to prevent similar tragedies.
In Richmond, several thousand people jammed a park at Virginia Commonwealth University as a distant church bell tolled 32 times across VCU's silent urban campus. Beneath the park's massive oaks, people stood with their heads bowed, tears welling in their eyes.
"As a parent, you just can't imagine what their families are going through," said Diane Willard of suburban Richmond. Her own two children attend a community college.
Nearby, James Verlander, a burly Richmond firefighter, shed tears and tenderly recited a Christian responsive reading. "If this doesn't hurt you, something's wrong with you," he said.
Memorial services were also held around the nation Thursday,. Nearly 3,000 students gathered at Western Kentucky University in Bowling Green for a vigil that included a banner that read, "Today We Are All Hokies."
Private funeral ceremonies were held Thursday for two international students killed in the massacre. Egyptian Waleed Mohammed Shaalan and Partahi Mamora Halomoan Lumbantoruan, a civil engineering doctoral student from Indonesia, also will have funerals in their home countries. A funeral was held Friday in Israel for professor.
As families mourned and began burying the victims, investigators worked on the evidence and looked into the warning signs in Cho's past, including two stalking complaints against him and a psychiatric hospital visit in which he was found to be a danger to himself.
The Brady Center to Prevent Gun Violence, the nation's leading gun control group, has charged that, reports CBS News chief investigative correspondent Armen Keteyian.
"If the current law on the books had been effectively administered and followed, this individual would not have been able to buy these guns."
According to the FBI, once a person is disqualified — "adjudicated," or judged, by a court to be mentally defective — "he/she is prohibited for life" from owning a gun.
The Brady Center says Cho met that legal definition when a special court-appointed justice declared that Cho "presents an imminent danger to himself as a result of mental illness."
But Virginia State Police tell CBS News that Cho was "not prohibited" from owning a gun because, despite declaring Cho a danger to himself, the judge did not commit him against his will to a mental health facility but instead ordered him to undergo outpatient treatment.
When Virginia gun dealers did the required background checks, Cho's name was not in the system — and he walked away with two very deadly weapons.
Today, the AFT, the federal agency responsible for regulating firearms told that its general counsel is reviewing whether the federal gun law was interpreted correctly.
Meanwhile, Police filed a search warrant for a laptop and cell phone used by one of the first victims,, who was shot in a dormitory.
"The computer would be one way the suspect could have communicated with the victim," the warrant said, but it offered no basis for a belief that Cho might have been in contact with her.