hello fellow stranger on the internet

thanks for clicking on my thread, much appreciated!

The movie that im searching is about a australian psychopath/killer based on a true story, I watched it when I was younger like 17 but I just cant find it. So if I remember it right it began with a couple out in the australian wild like camping or something, during their sexual interaction they are attacked by the murderer ( a fairly old man ). the boy gets killed immediately, the girl runs of and gets on the road stopping a truck. the passenger a man in his 30 or 20s gets out and tries to help her but suddenly he gets knocked down, he wakes up seeing the killer litt. butchering the couple, you see all the meat and stuff. the man runs off and escapes ( this is the first scene I remember the next is like in the middle of the movie) I remember him trying to escape with a new truck and the killer following on his big truck, he whistles on his flute like thing and kangoroos or something like get attracked by the sound and they get crushed by him while he laughs like crazy still following this person. ( next scene) the man eventually gets caught by the killer, he sits with him in his bunker type thing. He is tied up and gets asked history questions by the killer but if he answers wrong the killers chops of his finger. He anwsers wrong but claims that he cant be wrong bcs he is a history teacher implying that he is delusional. the killer chops of one of his fingers and when distracted the man frees himself and runs of. the killer laughs hysterically and frees his 2 dogs. the man gets trapped in of his booby traps and passes out while seeing the 2 dogs and the maniac in front of him. He awakes before a police station when the credits finally role with the full after story explained trough text which says that he survivied, its based on a true story.

So thanks for reading my explanation. Im really gratefull!

Pls if you recognise this movie pls leave a reply! it really stings when you just cant remember the movie if you know what I mean 🙁

thanx in advance!