1 Everybody considered Jane Doe, a witch
The girl was brutally tortured as it was believed that she was a witch. However, Tommy always believed that the girl should not be tortured as she is innocent.
2 Jane created hallucinations
As Jane wanted to make Tommy and Austin suffer, she created all the hallucinations that were seen by them.
3 Jane wanted revenge
Jane was tortured immensely in her life by many people. Now, she wanted to make people suffer by making humans see things and suffer.
4 Tommy decided to sacrifice himself
Tommy thought that if he would sacrifice his life for others' sake, then Jane's desire to take revenge with people will get over. This is what Tommy whispered in her ear and was being tortured by her.
5 Austin killed his father
Jane tortured Austin's father, brutally. As Austin did not want to make his father suffer more, he killed him. (See Triangle (2009) Movie Explained)
6 Jane killed Austin
The plan of Tommy did not work well as the cycle for taking revenge was not stopped by Jane. So, she continued taking revenge from others, including Austin, by making him listen to the sheriff's voice, which was nothing but the hallucinating sound. It resulted in the death of Austin as he broke his neck after he fell.
7 The cycle might go on again
The movie's ending intrigues everyone that there may be another part of the film as the cycle may not stop. There is a higher possibility for the cycle to be repeated as Jane's body was moved to a different place. (See Get Out (2017) Movie Explained)
8 Some suggest it was all in Austin’s head
According to some fans, Austin imagined everything to find an excuse to kill people, and Jane was a normal corpse. As per those fans, they thought Austin was getting rid of the guilt through hallucinations.