Any Survivor repairing a generator suffers from the Blindness and Exhausted status effect.  If the Survivor is already Exhausted, their status effects timer will be paused.

Both status effects linger for 5 seconds after stopping repairs.

After hooking a Survivor, THWACK! activates:

The next time you break a Breakable Wall or a Pallet, all Survivors within 28/30/32 meters of your location will scream and reveal their Aura for 4 seconds.

Each time a generator is repaired, all windows and vault locations within 32 meters of it are blocked for all Survivors for the next 30 seconds.

You become obsessed with one Survivor.  Your Obsession gains a 33percent action speed bonus to unhooking and healing other Survivors.  Each time you hook a Survivor other than the Obsession, if the Obsession is alive, gain a token.  If the Obsession is alive, all Survivors who are not the Obsession get 3percent penalty to repair, healing and sabotage speeds for each token.