Greenwich police have determined that no charges will be filed after completing their investigation into the suicide of a teenager whose death sparked concerns about bullying. Police said Friday that the investigation did not cover any ‘‘articulation’’ by Bart Palosz, 15, as to why he took his life. Palosz died of a self-inflicted gunshot wound in August at his family’s home after the first day of school. Police said that in suicides the motive often is not determined. A student club was established at Greenwich High School to end bullying after Palosz’s death. First Selectman Peter Tesei has said he was told by people who knew Palosz that bullying might have contributed to his suicide.