Why is there a だ in もっとだ?


I am watching a certain show at the moment where someone is talking about
wanting to kill evil creatures. Please don't judge this question as childish
just because the extract is from an anime.

He says

> くちくしてやる。この世から。一匹残らず

I understand that, but then he says

> **もっとだ** 。もっと。もっと殺したい。

I don't understand why he would say もっと **だ**. The reason why is that I don't
know what he is saying exists as 「もっと...」, if you understand what I mean. I
know the meaning of the word, I just don't get why he would say だ afterwards.
Like, if I asked in Japanese I would say... 何が「もっと」ですか？ What would replace 何
in that question?

Is だ just emphasis of how much he wants to kill more?




Pulling from <http://kurotoxxx.exblog.jp/20636377>:

> 駆逐、してやる! この世から、一匹残らず...  
>  I'll exterminate 'em! From this world, with not a single one remaining...
>
> もっとだ!  
>  More!
>
> もっと... もっと殺す! 殺したい。  
>  More... Kill more! I want to kill them.
>
> もっと、いっぱい... 殺してやる...  
>  With more, full-on-ness (for lack of a better word)... I'll kill 'em...

I believe "もっとだ" does emphasize the "もっと殺す" to make it stronger as "もっと" comes
immediately before "殺す" in the following sentence - I'm pretty sure "もっと殺す!"
needs to follow to make it clear what the "もっとだ！" refers to here.

"もっとだ！" by itself without following context could mean "give (me/it etc)
more!" in an informal and stronger way than "もっと！", or "it's more (than
something)" etc.

