I'm certain your movie is "Just Before Dawn". This is the only movie I
know of that features college kids, inbred twins, and a
fist-down-the-throat death scene.
"Probably the most beautifully shot and competently acted 'killer in
the woods' film from the early 1980s, Just Before Dawn is a must-see
for slasher fans...
A group of young men and women are traveling in a winnebago towards
the mountains. Warren (Gregg Henry) and his girl Connie (Deborah
Benson), Jonathan (Chris Lemmon) and his girlfriend Megan (Jamie Rose)
and Jonathan's brother Daniel (Ralph Seymour), drive past some locals
living in poverty. 'I wonder why there's so many twins around here?'
Daniel asks. Warren responds with an irreverent comment about
Roy McLean (George Kennedy), a forest ranger, lives in the area and
sees the them driving by his house. He comes out and demands to know
where the group is going. He's told they're going up to Silver Lake to
check out some land one of them has inherited. Roy gives them the old
'you've been warned' speech we've all come to expect in these
The killer is actually a set of twins!... The tree falls and the
grotesque twin comes after her with the machete. As he's about to
strike her, Roy shoots the killer...
Later, while packing up their stuff to leave... Connie has found the
inner strength to face danger. The surviving twin jumps out... Connie
musters up all the energy she can and...sticks her fist down the
The Terror Trap: Just Before Dawn
"Just Before Dawn" is available on DVD and VHS:
Amazon: Just Before Dawn DVD
Amazon: Just Before Dawn VHS
My Google search strategy:
Google Web Search: "just before dawn" inbred twins fist
I hope this is the right movie! If not, please request clarification;
I'll be glad to offer further assistance before you rate my answer.