Try bending the branches; do they bend or snap off and break?
Branches that are alive will bend. You can also do a bark scratch test.
See the article below.
Redbuds are susceptible to a couple of diseases that can kill a tree, quite quickly.
Also if your soil is poorly draining, root rot could be the cause of a slow tree or a complete die off.
Depending on the results of your tests on the tree, as described above. Give the tree a bit more time.