A firefighter is in critical condition after a violent altercation erupted inside the Whitehall Terminal on his way to Staten Island early Monday morning. Matthew Dugan, 34, who is assigned to Ladder 15 near the South Street Seaport, had to undergo emergency surgery to relieve swelling on the brain caused by the fight, which started around 1:30 a.m. as he entered the terminal with his girlfriend after drinking at a lower Manhattan bar. Witnesses tell police the fight started when three people laughed at Dugan's girlfriend after she tripped. One bystander tells the Post, "When they laughed, he told them to grow up. They said, ‘Shut the f—k up before we beat you up.’" The situation quickly escalated, and the assailants, described only as two men and one woman, began hitting him in the head and punching him in the face. Dugan, who was off-duty, didn't lose consciousness, but was bleeding heavily from his face and mouth when the ambulance arrived. One of his fellow firefighters tells the Daily News, "We're hoping he's going to be okay." And investigators are reviewing surveillance video showing suspects running from the terminal after the brawl.