Hi, 

This looks like a Norway Spruce tree (but many large evergreens get called a generic pine tree).

Did you or your neighbor have anything sprayed recently? If it was a type of herbicide it could have volatilized and drifted to the tree. 

Did you have anything power washed recently and it could have been sprayed with cleaning solution? It doesn't look like anything is near by to have that happen though. 

Did you have any yard work don e recently that could have cut into the root system?

Does that side of the tree face a busy street or part of the driveway where a large truck could have been close with its exhaust system?

Some of the common needle cast diseases of spruce trees don't exhibit these symptoms and why we are leaning towards some type of environmental factor as opposed to an insect, pathogens, or fungal problem. 

Emily