What does the phrase 「ああなんだべか」mean?


I came across this phrase from a video game.

After having a discussion, a boy named ナムジン left from the place and a guy who
still remained there with others said this sentence.

> はあ ナムジンさま どうして **ああなんだべか** …。

For my understanding, ああ means 'like that' so the phrase would probably mean
'doing something like that'.

Is it related to a certain dialect?

