Okay so my friends and I are going to be filming a horror movie soon and then I'm in charge of video editing, so I have a few questions.

Short plot for the part I'm inquiring about: Cops break into a serial killer's house to arrest him, searching through the house, he starts killing them one by one.

So obviously for a horror movie it has to be dark throughout the house to make it suspensfull so I'm wondering how I can achieve this, these are the possibilties I thought of:

1) Should I turn most of the lights off in the house we're using and just leave enough on to see what's going on?

2) Should I film in regular lighting like normal and then when I'm editing it make it darker (I have access to Sony Vegas, Adobe Premiere Pro 2.0, and Windows Movie Maker)

Or is there any other ways I should do??? and if editing is involved, please tell me how to with either Vegas or Premiere