Thank you for writing.

The is dying and it appears to be a sudden death as would be caused by a fungus.  The leaves that I see appear atypical for an oak.  Can you send me a picture of two mildly affected leaves lying on paper?

Regardless, this tree is not only dying, it may be becoming structurally unsound.  A certified arborist should be called to 

1) diagnose in order to guide future plantings 

2) assess similar nearby trees for signs of a similar infection and

3) to remove the tree. 

Hi Lori, 

I did not get the image. Usually this is because the image is too large. Shrink it to under 2 megs and try again.

Oak wilt definitely spreads. So if this is the diagnosis and if the other trees do not show signs of infection, then root intermingling should be cut when the tree is taken down.  https://extension.umn.edu/plant-diseases/oak-wilt-minnesota