I agree that you can buy illegal guns easily. Prohibition didn't work for alcohol and hasn't worked with drugs. A crazy person who wants to inflict this type of damage is not going to be stopped by a gun control law.
The problem with this debate is that the politicians who would craft any gun control legislation are people who oppose private firearm ownership of any type. This is why the NRA is so vociferous (sp?) in their stance. Gun control laws don't work. Anyone who is going to break the laws agains killing people is not going to be deterred by a law limiting legal access to guns. Any new law would only affect law abiding people.
This is a mental health issue, not a gun comtrol issue.