This looks like seven-sun flower (Heptacodium miconioides). Unfortunately, these shrubs/small trees are susceptible to a problem called Botryosphaeria canker, which causes branch dieback. Any type of environmental stress such as high heat, drought, excessive rain, and/or cold winter injury can leave the plant more susceptible to this fungal disease. Unfortunately, there is not much you can do. There is no effective fungicide control. You could selectively prune out the most damaged parts if desired. 

Christa