I had a Huey Cobra fly right over my apartment yesterday evening. Definitely at 400 feet or lower. He did a tight, steep banked turn then rolled out. My buddy's son was outside with me. He said, "I could see his face". I have no idea where he came from or what he was doing. I've never seen a military helicopter fly like that around where I live, let alone a Cobra. I can't do anything about hitting some jackass flying that low. This is the second time I've had to get my aircraft out of the sky like that. I had an F-15 fly UNDER my flight path about two months ago out at my buddy's farm. He was flying map of the earth. I'd say 100 feet above the trees. At about 700 m.p.h. Again, I was flying within regulations.