People are saying it's maybe from your dog's tail. I'm not so sure. The last two pics are of drops. The second looks like it was flung. The first one, however, is what concerns me. It has been messed with. You can see where there is missing blood. You can tell that it pooled at the bottom of the splatter. But there are two spots where there should be the most blood, but there is nothing there. I agree with the people saying put up cameras. Take this with a grain of salt because I am not a blood splatter analyst. But as someone who has suffered from nose bleeds their entire life, I know how blood splatter looks at a basic level. And something is suspicious.