Cerberus Mk 2 killing Exes with a damaged arm

Cesar stepped back. An ex grabbed his damaged arm, and he flung it away. One of the fingers trembled when he made a fist, and the wrist was tweaked. An ache throbbed deep inside it. But it worked.
He swung the fist around, and an ex’s skull exploded on impact. He grabbed one in each hand and hurled them back over the fence. A dead woman tried to wrap its arms around his waist, and he crushed its shoulder and neck between his fingers.

Excerpt From Ex-Isle, pg 618
Peter Clines
https://books.apple.com/us/book/ex-isle/id989619017