Could Risk Assessment Have Prevented Virginia Tech Tragedy?

The gunman who killed 32 students yesterday at Virginia Tech has been identified as Cho Seung-Hui, a resident-alien student originally from South Korea. The Chicago Tribune is reporting that the 23-year old showed signs of aberrant behavior before yesterday's violent shooting rampage. President Bush has ordered American flags flown at half-staff, and he's in Blacksburg, Virginia with the First Lady for a campus convocation. Republican Senator John McCain says the incident at Virginia Tech does not change his view that Americans have a constitutional right to carry firearms, except "to make sure that these kinds of weapons don't fall into the hands of bad people." We hear about a note reportedly left by the killer. Were there indications that he might turn violent? What about gun control?