Fishers are actually not a cat, but from the weasel family.
Excerpt from Wikipedia:
Conflicts
In some areas fishers can become pests to farmers because they will get into a pen and kill large numbers of chickens. Unprovoked attacks on humans are extremely rare,[7] but they will attack if they feel threatened or cornered. There have been a few instances of fishers preying on cats and small dogs. A study done in 1979 examined the stomach contents of all fishers trapped in the state of New Hampshire; cat hairs were found in only one of over 1,000 stomachs. While there is popular belief for more frequent attacks on pets, zoologists suggest bobcats or coyotes are more likely to prey upon domestic cats and chickens.
This summer our son saw a very large on on our patio. He said is was much bigger than our dog of 17 pounds. Mac is no longer let out alone at night, pre-dusk, (That's when Ben saw our local beast.) or pre-dawn hours. I'm sure you would laugh if you saw me patrolling Mac's yard with a baseball bat!
I sure hope that we don't get to see it again.
I've been told, they employ their blood curdling scream to flush out prey.