It's hard to say what is going on from afar but the tree looks extremely stressed. Has it been watered this year during the high heat and lack of rain?
Any information you can give us may help us understand what is going on but the leaves look dried out and scorched so we would start with asking how long the tree has been in the ground, when you noticed the problem, if you have been able to give it water during this period of high heat and drought conditions, if any chemicals (herbicides, pesticides, fertilizers) have been used anywhere nearby, if you see any damage to the trunk etc. 
You should be able to see a widening of the trunk before it goes into the ground, which is where the roots meet the trunk. If it goes in straight like a telephone pole, remove soil and mulch until you uncover the root flare. (While you're there, make sure that the wrap or metal cage around the root ball was removed at planting time.
Keep mulch pulled back from contact with the trunk and remove any that is deeper than 3 inches.
We can still see some leaves alive under the top layer so we would suggest supplemental water immediately. This page will tell you the best way to water, and how to manually check with a screwdriver and your finger to make sure the water is getting to the root area where it needs to be: 
https://extension.umd.edu/resource/watering-trees-and-shrubs/



Christine