Sounds in the night...

The wife and I were woke up this morning at about 2:30 with the most chilling odd sound coming from outside our open bedroom window. The wife had heard it last week some time before sunup (I was at work already) and tried to describe it to me over the phone. Well, now that I have heard it I can understand why it is so hard to describe; it is very weard! The best way I can describe it is like a pig squealing and cats fighting at the same time, but to me it sounded like only one animal/thing, not more than one.
The first time we heard it this morning it sounded like it was right outside our window, but it could have actually been in the neighbors driveway/backyard. We heard it for what must have been less than 30 seconds doing its squealing howling sound, then we both just laid there. It then started up again a short while later, and I finally said something like "I have never heard anything like that before". The reason I said that was because I believe I have heard the sounds of every animal that could/would be in this area like possums, raccoons, cats, coyotes, etc. I have lived most of my life in the country and spent enough time in the woods to think I have pretty much heard it all,... but not this, not even close.
So anyway, eventually around 2:50 I got up and closed the window. I then went and turned the back porch light on thinking maybe it would scare it away. A few minutes after that the wife and I were staring out the back window looking at our now well lit back yard (its usually very dark back there) and we heard it again. With all the windows closed it sounded different, and much farther away. It definitely wasn't in the yard because we could see pretty well now. This time, with a lot of the sound muffled, it sounded like it could possibly be a sound that a raccoon, skunk, or something like that could make, but still nothing I have ever heard before, and I have been around a lot of those type of animals. So in the end, I still have no idea what we heard, and it still makes my skin crawl thinking about it. It was that creepy.
If we ever hear it again, I am hoping I can capture the sound on my Blackberry... but if we are lucky, this will be the last time we hear it.