Prosecutors declined Friday to charge Ryan O'Neal with assault with a deadly weapon for firing a gun during a brawl with his older son earlier this year.
There was insufficient evidence "to prove this case to a jury beyond a reasonable doubt," said a report from the Los Angeles County District Attorney's office.
"Witnesses gave, in different interviews, conflicting stories" of what happened during the brawl, said Jane Robison, a spokeswoman for the district attorney's office.
Mark Werksman, O'Neal's attorney, said prosecutors did the right thing by declining to pursue the case.
"It's a tremendous relief for Mr. O'Neal to have this resolved favorably in this manner," said Werksman, claiming his client acted in self-defense.
O'Neal, 66, was arrested at his Malibu home Feb. 3 for investigation of assault with a deadly weapon and negligent discharge of a firearm. He was freed on a $50,000 bond.
The actor has said he fired a warning shot to scare his 42-year-old son, Griffin O'Neal, who had attacked him with a fireplace poker.
He said his son lashed out at him during a fight, but he ducked and the poker struck Griffin O'Neal's girlfriend, Joanna Berry, who was eight months' pregnant.
She received a serious eye injury and needed stitches for a facial cut, said Gloria Allred, an attorney who represented both Berry and Griffin O'Neal.
Werksman said Ryan O'Neal suffered bruises to his arms and legs when he was struck several times.
Allred said prosecutors never considered filing charges against Griffin O'Neal in the case.
"There was no evidence to support that allegation that he, in any way, committed any criminal conduct," she said.
Since Ryan O'Neal won't face criminal charges, Griffin O'Neal and his girlfriend, "will now explore all of their legal options," such as a lawsuit, Allred said.
She also said Berry gave birth earlier this year and the couple was busy "focusing on their new baby, loving their baby."
The father and son had clashed before.
In 1983, police were called to their home after a fight in which Ryan O'Neal knocked out two of Griffin O'Neal's teeth, the Los Angeles Times reported. No charges were filed.
Griffin O'Neal also has had several run-ins with the law. He was found guilty of reckless boating in a 1986 accident that killed the son of film director Francis Ford Coppola, and later was given an 18-day jail sentence for failing to perform community service ordered in that case.
He also has pleaded no contest in two unrelated cases to drunken driving and shooting at the unoccupied car of an estranged girlfriend.