What the Heck?

I just walked outside and heard a jet flying low over my house. This isn't that unusual, being in Seattle, but it sounded strange. I looked up and saw only a large business jet at first. Then I noticed that a fighter jet was right beside it. That's what sounded so strange, I guess. They were flying very low. I couldn't make out what type of fighter it was.

Anyway, it's probably nothing.