Did someone throw a rock at my window?
That pattern indicates that a blunt object hit it, something relatively soft and larger. A rock or other hard and small object would leave a clear indicator like the picture below, with a central point and circular lines. What larger and blunt object would hit a second level window? Probably a bird. I think that this is a bird strike in the middle of the glass

As an interesting side note, here's an eagle that flow through someone's window last month