Your tree appears to be quite young. (Perhaps 16” diameter was a typo?)

The trunk appears almost corrugated. And, with the large number of bare branches at the top of the tree, I suspect it has not received sufficient water to help it establish a sturdy root system. More than likely, it was short of water even before you moved in. Then, the excessive temperatures of 2018 and lack of supplemental water that year added to the stress.

Newly planted trees require regular additions of supplemental water during the first 2 years. Many trees will continue to require additional water during the dry months, typically once a month. Each irrigation must moisten the entire rootzone to at least 8 inches.

You might try an easy test to determine if rooting has had a good start. To do so, grip the trunk at chest height, then rock the tree back and forth as you watch the soil around the trunk. If the soil moves, even the least little bit, the tree hasn’t started to root in. Sufficient supplemental water during the next 2 years may help it survive and, ultimately, thrive.

If the soil at the tree’s base doesn’t move when the tree is rocked, rooting has started but is likely to be limited. Regular supplemental irrigation through this summer and next may help the tree. (Because you mentioned it is probably an ornamental flowering tree [perhaps cherry or plum], it will continue to need water at least monthly for the rest of its life.)

Whether or not the tree is rooted in, I suggest you increase the current mulched zone outward to just below the branch tips. Then maintain a deep mulch of coarse material (similar to what is already present) to a depth of 3 inches.

Do not fertilize the tree. Our local clay soil is rather rich in fertilizer elements. Trees and other woody plants thrive here with sufficient water plus a thick mulch.

This year, do not prune what appears to be dead because you may inadvertently remove healthy wood. If you think you must prune, wait until after the leaves have fully expanded next year.