Madonna's ex-husband blew up at a someone trying to take his picture at the St. Regis Lobby Bar on Tuesday. The two-time Academy Award winner, in town to speak at the Salesforce's Dreamforce 2013 conference currently occupying eastern SoMa, was lounging at the acclaimed bar when he saw a flash go off and realized someone was snapping his mug. He then lost his collective shit.

TMZ has more:

A witness at the bar tells TMZ ... Penn bolted after the guy (who wasn't a paparazzo) ... and screamed at him, "Do we look like f**king zoo animals?"

Penn -- who was in town to speak at a sales conference -- also grabbed the man's phone and slammed it to the ground.

That's when our video begins ... and you can hear Penn yelling, "I'll make you eat the phone ... get the f**k out of here!!"

Mr. Penn later told hotel management, "You should do something about that." And as for the photog/fan, he reportedly refused to press any charges.

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