Airdate: 04/29/07 Every year, an estimated one thousand homicides are committed in the U.S. by people with mental illness. In April 2007, Seung Hui Cho became one of those killers when he shot 32 teachers and students at Virginia Tech, using two guns he'd purchased with no trouble. It's not supposed to be that way. Federal law bans the sale of firearms to people with severe mental illness, but the law has never been properly enforced. How can that be? Steve Kroft investigates.This product is manufactured on demand using DVD-R recordable media. Amazon.com's standard return policy will apply.