I was on AA #693 DFW-SAT Saturday on a segment run when we had a seating mishap occur during boarding. Two people having the same seat on row 8. The FA attempted to resolve the matter and then the GA came aboard and asked the seated passenger for his boarding pass and he refused to provide the documentation. When the GA asked him to then leave the plane he also refused. A police officer later comes aboard the plane and asks the man to stand up and he once again refuses. As the officer calls for more assistance, passengers start to abandon their seats around the passenger fearing an inevitable confrontation. Meanwhile, the pilots evacuated and lock the cockpit door as the police gather on the passageway. The situation is getting very tense. Then the #2 FA approaches the passenger once again and knells beside him in the aisle trying to establish a relationship with the man. With great patience and compassion she established a report with the gentlemen and minutes later he produced his boarding pass and the flight continued without further incident. I’d like to give special kudos for the flight attendant, which I did over GoGo, for giving the man an extra chance and intervening when she did. She could have easily walked away from that stressful situation and let the authority’s handle it. Instead she went the extra mile. It turns out the traveler was an adult special needs passenger. After the flight landed the pilot walked him off the plane and called his guardian who was there to pick him up. They meet in the security doorway exit as the TSA held the exit door open for them to discuss what happened. As they were talking, the flight attendant who helped was leaving the airport and the pilot introduced her to the man’s family. They were in tears grateful that the FA had intervened on their son’s behalf and a potential crisis was avoided. Sorry I did post this on another board that I've have been at for 5 years. It was to good not to share here at my new home. I was just approved here yesterday so this is my first post.