Police say a 17-year-old girl was RAPED at a KEITH URBAN concert on Saturday, at an outdoor amphitheater in Mansfield, Massachusetts, 30 miles south of Boston. And it happened in front of a large group of people on the upper lawn.

People who saw it took photos and video, and eventually a female fan ran over and pushed the guy off the girl. Other people say the guy got up and left on his own.


Either way he ran off, but was caught and arrested a short time later. He's 18-year-old Sean Murphy, and he's been charged with rape. He pleaded not guilty, and was released on $10,000 bond. 


His lawyer says the whole thing was consensual, and quote, "This was a private act, that regrettably occurred in a public place."


He also says the girl wasn't drunk or on drugs at the time, but Murphy has admitted to being "drunk on Jack Daniels and beer." And the police report says that when he called his parents, he was overheard saying he "messed up." 


This is the same concert police called a, quote, "mass casualty" event . . . more than 50 people were placed in protective custody, and 46 were given medical treatment. Mainly because they were all HAMMERED.


And right afterward, Keith posted a video online talking about how crazy the show was. He said, quote, "Up on the lawn tonight, that was nutso. It was so cool." Obviously that was BEFORE he knew how bad it was, or that someone had been raped.


That video has been removed.