invasion of the flies

The warm weather at the last couple of days has somehow brought an invasion of flies into my apartment. I've been trying to rid of them spraying Windex on them...and just as I thought I've gotten rid of the last fly, I see another one, then another one, flew by. It's driving me totally insane. I don't even know where they come from either!!

I'm usually not violent and I don't blog about pesky insects. But I think I'm at the point that I wish I have a shotgun of some sort and do this:

OR...any suggestions on getting rid of flies would be much appreciated.

credit: Little Project, a really awesome street project that is worth checking out.