What's the name of this Korean film?

We watched it at a Korean Club movie night up at school. It features a serial killer who grabs prostitutes. He kills them by ramming a spike through their head - he says it's more humane, because it's quick and that's how they kill pigs. One of the last victims actually gets out of his death basement and runs to a convenience store for help. The worker there calls the police, but by the time the main cop actually gets there, the serial killer had followed her and killed both the escaped victim and the worker. I don't remember what it's called, and I bought "H" thinking that might be it, but they are in fact totally different movies. Do you happen to know?