What to do if someone commits Suicide and in suicide latter written yo

As male has caught his fiancé talking to her ex-bf over calls. The male person had previously asked his fiancé about the same on which she told that she is in no contact with her ex. Can a male be held guilty if the girl fiancé commits suicide by writing his male fiancé name in suicide note after breaking the engagement? If so how can he overcome and protect himself?