The shooting: guns

Been wondering about the technical details of shooting in Virginia Tech (and feeling faintly guilty about it).

The news reports say that the guy had a Glock 19 and a Walther P22. I keep wondering how many rounds of ammunition he has fired. Killing 33 people and wounding about as many with two handguns takes an awful lot of ammo. How many did he fire? How many did he have? Were they in preloaded magazines? Was he using the extra-large (33 rounds) magazines for the Glock?

The whole thing just seems like such a lot of work... If I were a psychotic killer intending to shoot 60+ people, I'd buy at least 500 rounds, start preloading all of them, lose my enthusiasm for the project at about round 100, and after loading 150 I'd say "bugger it, my hands are really sore, I need a beer", and postpone the whole thing indefinitely. (Note to self: psychotic killing is obviously not your thing.)

Why did he file the serial numbers off if he intended to kill himself? And considering that he did file the numbers off, why did he keep the receipt?

Oh well, he was a deranged mass murderer, which probably explains a lot.