Whether the Manbij attack was caused by Turkey backed FSA, by the Turkish secret services MIT, or by ISIS, is irrelevant. They are the same. Same goal

Two US soldiers and a fighter of the Manbij Military Council were killed by the explosion in Manbij City. The perpetrators are believed to be sleeper cells of Turkish-backed jihadists
Whether the Manbij attack was caused by Turkey backed FSA, by the Turkish secret services MIT, or by ISIS, is irrelevant. They are the same. Same goal