Questions about this sentence

Question

"当時の関係者何人かにあたって記憶を確かめてみたが、人の記憶の欠落部分というのは、捏造で補われる仕組みになっているらしく、共通の体験が、しばしば、お互いに矛盾する記憶になっていることに驚かされた。"

What does "にあたって" mean there ?

"驚かされた" is referring to what/whom exactly ?

Does "関係者何人か" mean "Some people of the authorized personnel" ?

Answer 1

To supplement @istrasci's answer:

あたる here is the 4th entry in the article on goo 辞書, basically "investigate" or "observe".

Answer 2

The whole sentence basically translates to something like

(I) Tried to verify the memories of the related parties of/at the time, but I was surprised to learn that when it comes to the "holes" in the human memory, their recollections of the same/shared experience were inconsistent with each other, almost as if it was all setup -- (the memories) fabricated to complement one another.

• 関係者何人か means "several of the people related to <whatever the context is about>".

• The 驚かされた is referring to whoever "speaking" that sentence; presumably the person that questioned these people about their memories of whatever happened.

I know what 〜にあたって means when it has the sense of 〜の時, but that doesn't make sense here. So I'm not sure why it is used in this sentence.