Never cut in front of a Semi ? | Tesla dashcam observed a live car accident | Who's at fault ??

During my Boston - Canada roadtrip back in April. I have observed a car accident and it was captured by my Tesla's dashcam. Let's walk through this accident and I have some questions and recommendations after observing this crash ! Definitely leave your comment and share your toughts.
#sentrymode #tesla #dashcam #caraccident

[@W8TLS]

If you can't see the semi driver in his mirrors, He doesn't see you.