Well.. Honestly (being a non-american) I cannot understand why you would think an incident such as this will really move people to pass an ammendment outlawing guns.

As I understand your system, such a proposal would have to first:
pass the house of representatives (representatives are sitting for periods of 2 years, so they're almost always "on campaign" in some way or another, thus they're unlikely to pass unpopular bills)

-IF- it passes, then it'll have to pass the Senate (senators are sitting for six years in a row, so they're more likely to make unpopular decisions [which may be wise!] )

Even if it passes the senate, then the president could refuse to let it pass, in which case it must go back to the senate and two thirds of the senate would have to vote yes to passing the bill in order to make it pass.

Now. As I understand it, the republicans are most often in favour of giving the citizen the right to arm himself while some (maybe the majority?) of the democrats would appreciate if that right would be suspended -- because, as you point out, guns are often used to harm people.

Now.. With that in mind. Don't you honestly agree that the chances of outlawing guns look bleak to say the least ? You can be almost certain that Bush would use his veto-rights and it's doubtful (to say the least) that two thirds of the senate would let it pass.

Anyway, just my two cents.