If a Tree Falls (2010)

Siblings Brad and Lisa Carpenter, along with two lifelong family friends, Will and Vanessa, set out road-tripping to an annual family reunion. They make the decision to find a place to stop and camp for the night. What ensues is a violent disturbance by six masked assailants, without motive or reason. The group finds themselves living a nightmare of psychological games and physical terror; as morning dawns, the reality of what will come is more horrifying than anything the group could have ever imagined.