When take the context of the film - which gives some inclination of it's savagery in the opening scenes - the wild wilderness of the mid eighteen hundreds, no doubt such cruel ness existed, so maybe did such creatures too as depicted here.
However, I too was unprepared for the slaughter scene which totally knocked me sideways, the imagery stayed with me for days.
Not sure if that was to add shock value to a - what appears to be a low budget film, with relatively unknown Actors with the exception of Kurt Russell.
But it was a well produced little film, kept you glued to the screen, even if it
did contain was one of the most brutal scenes probably in film history.
Be warned - you will be shocked....