In the clip, released by Entertainment Tonight, LaBeouf, 29, and Goth, 22, are arguing on the street when locals intervene.
"I don't want to touch a woman, I don't want to hit a woman, but I'm being pushed," LaBeouf tells the German men, before accepting a ride from them to the airport.
The actor then approaches Goth and asks for his backpack, telling her, "I don't wanna touch you. I don't wanna be aggressive. This is the kind of s--- that makes a person abusive."
LaBeouf then proceeds to get in the car of one of the locals and travels to the airport.
The camera keeps rolling as the star makes a shocking statement.
"If I'd have stayed there, I would have killed her," he tells the men.
During the car ride, LaBeouf puffs from what appears to be an e-cigarette and discusses guns with the German locals.
The actor even appears to attempt to make a FaceTime call to his Transformers costar Megan Fox.
When the car arrives at the airport, LaBeouf offers to host the men if they ever visit Los Angeles.
VIDEO: Rap Crew Says Shia LaBeouf Ripped Off Their Lyrics in Freestyle Video
LaBeouf was reportedly visiting Goth, whom he's been dating since 2012, in Germany, where she's shooting Gore Verbinski's A Cure for Wellness.
LaBeouf's rep did not immediately respond to a request for comment.
The pair first met while filming Lars von Trier's NC-17 drama Nymphomaniac: Vol. II.
The Fury actor has exhibited increasingly strange behavior over the past few years. In an odd video released last month, the actor, shirtless, sports a rat tail as he performs a freestyle rap that a group later claimed as their own.