The non-suicide - Detective Riddle

A body is found at the bottom of a high-rise block of flats. To the untrained eye, it looks as if the person had taken their own life. Detective Mehul goes to each floor and finds the window looking out to where the body is. He flips a coin when he opens each window. Once he has done this on every floor, he deduces that it wasn't suicide. Why?

None of the windows were open. If the person jumped, who closed the window? None of the windows were open. If the person jumped, who closed the window?