何が起きてるのか

what's happening

→ 何
phrase Rare #32,976
what's happening An embedded question meaning “what is happening” or “what is going on.” 起きてる is the casual form of 起きている, and のか marks the question within a larger sentence.
JA: 何が起きてるのか、まだ誰にもわからない。
EN: No one knows what's happening yet.

ここで何が起きてるのか知りたい

I want to know what's going on here.

何が起きてるのかわかってる

Do you know what's going on?

責任者なら何が起きてるのか教えるべき

If you're the person in charge, you should explain what's going on.

— REC / レック (2007)

何が起きてるのか察しついてた

I had a pretty good idea what was going on.

彼は何が起きてるのか分かってなかったんだ

He had no idea what was going on.