GENE HACKMAN knew the homeless man he slapped earlier this week outside a restaurant in Santa Fe, New Mexico.

Gene and his wife have a home in Santa Fe, and he told police that he'd given the guy clothes, money and rides over the past few years.

According to the police report, the chaos began when the man, 63-year-old Bruce Becker, approached Gene and his wife and asked for money.

Becker claims Gene called him a WORTHLESS BUM and told him to get a job.  Then he replied, "Gene, you are just another Clint Eastwood, you are nothing but an empty chair."

That allegedly set Gene off, and he supposedly started PUMMELING Becker, hitting him 10 or 12 times.

Gene's version of the events is a little different.  He admits he told Becker to get a job, but says he tried to walk away.  Becker followed, and called Gene's wife a derogatory name. 

Gene says that when Becker approached them in a threatening manner, he hit him ONCE to back him off, and they both fell to the ground.

Whatever the case, cops believe Gene acted in self-defense, and they're not going to charge him.