Just Before Dawn (1981)

Storyline:

Just Before Dawn (1981) Five campers arrive in the mountains to examine some property they have bought, but are warned by the forest ranger Roy McLean that a huge machete-wielding maniac has been terrorising the area. Ignoring the warnings, they set up camp, and start disappearing one by one. If that sounds too run-of-the-mill, there's a genuinely shocking plot twist half-way through...