Penn, 56, ripped into musician Jimmy Giannopoulos in front of ex-wife, Robin Wright, prompting her to burst into tears!
Sources told RadarOnline.com the three had enjoyed a quiet dinner at Le Gamin, a classic French café in Brooklyn, N.Y., on May 30, and then headed outside.
Milk star Sean crouched in front of them, and then inexplicably exploded!
"Sean had his cell phone in his hand and held it up to Jimmy's face to show him the screen," an eyewitness spilled to RadarOnline.com. "A heated exchange followed, and Sean's face got redder and redder as he confronted Jimmy with whatever was on the phone."
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Soon enough, Penn began yelling at Giannopoulos and pointing at him angrily!
"At one point, Robin broke down in tears, and Sean comforted her with a hug and held her hand," the source continued. "Eventually, all three calmed down, and someone met them on the sidewalk, carrying their luggage."
Sean and Wright were married from 1996 to 2010. The couple also has a son, Hopper, 23.
After their divorce, Sean moved on to a high-profile romance with Monster actress Charlize Theron, 41.
And despite his ugly public outburst, the source said Sean parted on friendly terms with Wright and Giannopoulos.
"Things seemed to have ended amicably, as the trio hugged before going their separate ways."
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