Police Believe Gabriel Aubry Started Brawl But He Won't Be Prosecuted

Law enforcement sources tell TMZ ... detectives are now clear on what they believe happened -- Gabriel committed two batteries on Olivier Martinez before Olivier lifted a finger to defend himself.

As TMZ first reported, as Gabriel deposited Nahla at Halle's house Olivier walked out and said, "We have to talk."

Based on interviewing the principles and witnesses, detectives have concluded Gabriel then pushed Olivier (battery #1) and swung at his face, making contact with his shoulder (battery #2).

Cops say at that point, Olivier responded in self defense with 3 quick punches to the face.

What's more, law enforcement sources tell us they are "concerned" about what they believe are "Gabriel's ongoing anger issues."

As one law enforcement source put it, "It seems he's still having a hard time getting over his break up with Halle."

But here's the good news for Gabriel -- we've learned Halle and Olivier have both told detectives and prosecutors they do not want Gabriel charged with a crime because they do not believe it would be in Nahla's best interests.