Though it's unclear if he told anyone about his plans to stage a shooting rampage at Virginia Tech, from childhood, Seung-Hui Cho showed an appetite for brutality, according to a new report.
The Washington Post reports that while Cho was unusually quiet as a child -- according to relatives, he refused to respond to greetings and didn't want to be hugged -- when he fought with his older sister, Sun-Kyung Cho, his actions spoke volumes. Relatives say he punched her with shocking force.
Despite signs of trouble, Cho's mother didn't seek treatment for him because he did well in school, the Washington Post reports.
But in their first public statement since the massacre, on Friday, Cho's family said that their son "has made the world weep" and that they are now "living a nightmare."
The statement, released to the Associated Press by Sun-Kyung Cho, says the family feels "hopeless, helpless and lost," after the 23-year old Va. Tech senior took the lives of 32 people.
"We are humbled by this darkness," wrote 25-year old Sun Kyung Cho. "This is someone that I grew up with and loved. Now I feel like I didn't know this person ... My brother was quiet and reserved, yet struggled to fit in. We never could have envisioned that he was capable of so much violence."
But there are signs that Cho's family, or others, could have known he was plotting a massacre.
On Friday, ABC News obtained court documents that show police are probing the possibility that Seung-Hui Cho may have confided his plans to someone else. In a search warrant affidavit filed by Virginia State Police Friday, authorities say the shooter "may have communicated with others concerning his plans to carry out attacks on students and faculty at Virginia Tech."
The affidavit also revealed that Cho kept up contact with his parents, saying, "an interview with Seung-Hui Cho's family revealed her often used a cellular telephone to communicate. He normally spoke to his parents on Sunday evenings."
Police are now seeking Cho's cell phone records from Verizon Wireless in New Jersey.
In another warrant affidavit filed Friday, police seek to mine Virginia Tech's computer servers, to see if Cho may have communicated by e-mail with Emily Hilscher, one of two victims shot in Ambler Johnston Hall.
The affidavit says that "there is probable cause to believe the computer information maintained by Virginia Tech for Seung-Hui Cho and victim Emily Hilscher, may contain information relating" to the shootings. The warrant also cites a criminal investigative analyst who tells police "that in 80 to 85 percent of homicide cases the victim is known to the offender."
On Thursday, Virginia Tech police seized Hilscher's laptop computer and her cell phone.
ABC News also learned police have obtained a medical and a counseling file for Cho from Schiffert Health Center at Virginia Tech, suggesting the 23-year-old killer may have worked with campus counselors -- something that has not yet been confirmed by university officials.