I'm not much with shrubs, but first thing to do is definitely get in there inspect the damage closely. To me it looks almost like herbicide or other toxic liquid was splashed just in those sections. It could also be broken branches from damage, etc. You might also see if those branches belong to one plant while the other healthy ones belong to other plants?
Look closely at the dead branches -- at they actually dead? Are they dry and snap when bent? Are there signs of sucking pests?
I'm thinking If the damage is due to pest infestation, then the infested branches should be cut off, if they are dead, then cut off to healthy, living branch, but if they are alive and not infested with temporary leaf loss, you might want to just shake or pull off the dead leaves, then cut back just a little bit to allow the branches to grow new leaves.
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