In watchmen why does rorschach whre the mask?

In the graphic novel he worked at a dress shop. A young woman asked for this dress but found it ugly afterwords. That lady turned out to be Kitty Genovese who was brutally raped outside her apartment while neighbors did nothing about it(real life incident). Sickened by this, he takes the dress, cuts it into a mask and wears it. During the beginning of his vigilante crime fighting he was merely Walter Kovacs in the mask, but after the kidnapped girl incident he sort of went crazy and claimed his real persona to be Rorshach. I might be missing things as I haven't read the GN in ages, but that's pretty much it.