On the sidewalk outside his Oakland home, Gabriel Shin held up his left arm to shield his head from the incoming blow.
A man wearing all black swung a 15-inch spanner, a wrench used to open hydrants, toward the veteran San Francisco firefighter. It connected with his forearm, snapping the bone. The wrench hit his face, sending his glasses flying and leaving him with a concussion.
“You motherf—,” Shin yelled…