The report of the private investigator hired by Angelina Jolie was the last straw which prompted her to end her 12-year relationship with Brad Pitt.
While rumors have been going around for long that the actor has been in an affair with his French co-star, Marion Cotillard, the report confirmed such speculation.
Pitt, 52, and Cotillard, 40, were together in London for months to shoot the World War II film, "Allied".
It was said that Jolie was disturbed by some of the film's romantic scenes.
According to FOX News, a source close to Jolie said the actress hired a private investigator as she was having this feeling that her husband has been " fooling around " with Cotillard on the set .
It turned out he indeed was, based on the private investigator's report.
Aside from cheating, Pitt was also discovered to be "partying like a single guy on a mission."
Jolie, 41, cited their "irreconcilable differences "as the ground for filing the divorce.
The Daily Mirror reported that Jolie kept on reminding Pitt that he is no longer in his 20s, given the many accounts of the actor's "boyish antics." Other concerns were related to his drinking and pot-smoking.
It was also described that their marriage appears to be already on the rocks before Jolie's discovery of Pitt's unfaithfulness as Angelina stayed in New York and Pitt attended Le Mans race in France on Father's Day this year.
Meanwhile, the Oscar-winning Cotillard has yet to give her statement regarding the reported affair, although a source describes that the actress was devastated for sure with her involvement in the Brangelina divorce.
This is not actually the first time that Pitt, a multi-awarded actor, was being linked or reported to be romantically involved with his co-star.
