You don't mention how long the tree has been in this location but it appears to be fairly new. It may be that the tree has struggled to establish. I would pull back the landscaping fabric that you have over the root zone of your tree. These types of fabric can stop gas exchange between the soil and the atmosphere which is necessary for the survival of plants. You'll also want to pull back the mulch from the base of the tree as well as soil, until you reach the uppermost root. Next, cut back the portion of the tree on the top that is dead, just above the top living shoot. Remove the shoot that is coming from below the graft at the base of the tree. You'll want to make sure the tree is staying irrigated and gets about 1" of water per week through either rainfall or irrigation. This is especially important considering that we are entering a droughty period. You can measure the amount of water using either a tuna can or rain gauge. Any container with straight sides will work.

The tree may recover in time if you can give it a fighting chance.