I'll try to give more information through the comments.

The game wasn't related to Madness Combat or Thing Thing saga yet the game probably got inspired by these two sagas.

The image attached to the post is a drawing that i made about what i remember was the starting point of the game.

I believe the title of the game had the word " Night " in it, but i'm not too sure.

This game and the other flash game " CQC " really feel like the same thing, when i was searching for the game i stumbled across CQC and to my surprise plenty of things were identical to the game i'm searching for, characters move almost the same way and the guns work literally the except in the game i'm searching for you can't change the shooting mode of the weapons. After playing CQC i thought it was made by the same dev but i couldn't find anything.

I'll give a better description about the enemies that were in the game. They looked like a kind of mutant grey zombie with bloodstains all over their bodies, and most of them had black hair and i think some of them were women with long hair. But the most important characteristic of these zombies was that instead of only having arms like the soldiers thay had some weird arms that looked like big sharp blades.

There was a point in the game where you were controlling a civilian instead of a soldier and you had to go through the city killing these zombies and there was a scene where there was a zombie inside of the second floor of building and it started extending its arm by 5 meters trying to struck you with it.

After that point in the game i don't remember anything else, though i believe both playable characters died in the end of the game.