I'd let it go for a while, and when you're sure the upper parts are dead, cut them out and let the new growth take over.

it is .. most likely not a grafted plant... so it might come back from the roots ... but as lacy notes.. that could take half the summer.. so be patient ...

it seems planted to close to the fence... its not going to stay that size forever ... you planted it according to the size it was in the pot, and most things have a lot more potential ... and it would be better to plan for the future.. rather than battle it on the fence ... i would plan on moving it in fall .. after it loses its leaves.. presuming it leafs out ...

if you have a warranty .... perhaps it isnt worth waiting to find out.. if the root mass is still alive .. if not.. then just be patient ...

ken

Looks like a carcass to me, I'd replace it with something else.

Especially if the problem is pathenogenic, you don't want to keep a dead/severely compromised shrub around.