Mod Installation Guide
Required Tools:

ScriptHookV: http://dev-c.com/gtav/scripthookv/

-ScriptHookV allows custom scripts to run in GTA 5. Download the latest version here.
-Put all files into GTA 5 game directory.

ScriptHookVDotNet: https://github.com/scripthookvdotnet/scripthookvdotnet/releases

-ScriptHookVDotNet enables you to write and run .NET scripts. Make sure you get the -most recent release.
-Put all files into GTA 5 game directory.

NativeUI: https://gtaforums.com/topic/809284-net-nativeui/

-NativeUI provides a framework for creating user interfaces like menus in GTA 5 mods.
-Put all files into scripts folder.

Mod Description: Friendly Fire
What the mod does:

The Friendly Fire mod adds the ability to fire at your teammates or characters that are normally protected from fire. This mod removes the restrictions that prevent you from causing damage to allies or characters near you, adding a new level of challenge and realism to the game.

Installation Instructions:
Create a "scripts" Folder:

If you haven’t already, go to your GTA 5 game directory and create a new folder called scripts.
Place Files in the "scripts" Folder:

Download the required tools listed above.
Extract all necessary files from the downloaded archives and place them in the scripts folder.

Enjoy the Mod:

Start the game and enjoy.