Investigators pressed ahead Saturday with their search for Virginia Tech shooter Seung-Hui Cho's motives, even as more of his victims' families prepared for memorial services. Authorities sought Cho's cell phone records on the chance he warned someone about what would become the nation's worst mass shooting in modern history.

"Seung-Hui Cho is known to have communicated by cellular telephone and may have communicated with others concerning his plans to carry out attacks on students and faculty at Virginia Tech," police wrote Friday in an affidavit seeking records from Verizon Wireless.

Police also continued their hunt for a connection between Cho and Emily Hilscher, one of the two victims killed at West Ambler Johnston Hall, seeking search warrants for the students' Virginia Tech e-mail accounts.

Another affidavit sought Cho's records from the student health center, and police obtained his medical and counseling files. The contents of the warrant affidavits were first reported by ABC News.com.

Meanwhile, friends and relatives of Hilscher and Ryan Clark, the other student killed at the dorm, were to memorialize them Saturday at services in Virginia and Georgia. Services also were set for Reema Samaha, one of 30 students Cho killed at Norris Hall, a classroom building.

The family of Cho, who committed suicide, slipped back from the spotlight a day after issuing a powerful statement apologizing for his actions.

Sun-Kyung Cho said she and her parents are "living a nightmare."

"We are humbled by this darkness," she wrote in a statement issued Friday to The Associated Press. "We feel hopeless, helpless and lost."

It was the Chos' first public comment since Monday's massacre.

"I actually feel sympathy towards their family," said Virginia Tech freshman Andrea Hacker, 19. "A lot of people are probably looking down on them now, but they have no reason to.

"It's got to be tragic for them as well. They're going through just as much grief as we are, plus the added pressure of having a brother do this."

The family's statement was issued during a statewide day of mourning for the victims. Silence fell across the Virginia Tech campus at noon and bells tolled in churches nationwide in memory of the victims.

Cho's sister said her family will cooperate fully and "do whatever we can to help authorities understand why these senseless acts happened. We have many unanswered questions as well."

While Cho clearly was seething and had been taken to a psychiatric hospital more than a year ago as a threat to himself, investigators are still trying to establish exactly what set him off, why he chose a dormitory and a classroom building for the rampage and how he selected his victims.

Seven people hurt in the rampage remained hospitalized, at least one in serious condition.