The author shows authority by saying that hey know people who were hurt by the tragedy directly.
Step-by-step explanation:
The author of the text is able to assert their authority over the text and its subject matter on the Jews by asserting that they have some personal ties tot he event.
They know the people who have been hurt in the holocaust thus they are able to give some information and that will be relevant to them.
One would wonder however, how only the personal contact of the author with the tragedy must give them authority and not them being author only.