I would stay upstairs and call the cops. Lives are more important than objects and you never know whether the burglar would become violent or not.

It's smarter to stay upstairs, but I think the natural instinct is to check things out. Especially because you know there's most likely a logical explanation and that its probably not a burglar even though it's your first crazy thought. And no one wants to call the cops when it was probably the cat or something that fell over. So I understand op going to check things out first, especially because she owns a cat. It's a different story if you hear glass break, things being moved around, with footsteps, possibly even seeing a flashlight. Probably best to wait a minute to hear if there are footsteps or not. But if you own an animal you probably always assume it's the animal. So understandable on op's part.