Water coming from Top window

[Daniel Suarez]

Hey All, 

Pretty bad rain here today and I realized that water is coming from the top of the window (see picture) Any idea of where that must be coming from? What kind of professional should I hire to help me investigate (or is it something I can do) I'm thinking a loose siding? or maybe dirty gutters letting water in? 

By the way this window faces west from inside the house towards the street directly. It is in the main floor of the house (middle between top and basement)

I have exactly the same problem in the basement even though there is a deck on top but that's a different matter.

Thanks in advanced.