Robert Michael OHare Jr May 6 1952 September 28 2012 was an American actor who performed on stage and television He was best known for playing Commander Jeffrey Sinclair in the science fiction television series Babylon 5 a role he left due to serious mental health issues Born in Chicago Illinois He attended Chicagos Mendel Catholic Preparatory High School then studied at Harvard University where he majored in English literature He studied at the Juilliard School of Drama and with Sanford Meisner