CENTRAL ISLIP - A Farmingville teen was arraigned today on charges he murdered a young Holbrook father who had served in the Iraq war. Robert Gregory, 19, has been charged with second-degree murder in the stabbing death of Julian Pena. Police say Pena was killed in the parking lot of Momo's sports bar on Union Avenue early Wednesday morning. Pena, a six-year Navy veteran of Operation Freedom, was stabbed when a fight broke out between two groups of people outside the bar, investigators say. Gregory has a long rap sheet that includes assault and drug charges and probation violations. His attorney says he doesn't believe his client knew the victim. Gregory is being held without bail and could face 25 years to life in prison if convicted. Ruben Rosario, 28, of Selden, has also been charged with gang assault in connection with the deadly attack.Arrests made in stabbing outside Holbrook bar