How can i make a viewmodel like nico's nextbots?

So, I want to make a horror game. But when the character is running, I want to show the viewmodel and make an animation like Gmod. I couldn’t find anything about this. I tried to use the fps pack with viewmodel codes inside. But it requires a gun so it didn’t work. Can you guys help? If you still didn’t understand, there is a sample video below:

I want to have a go at this, but I just realized I have no idea how I’d do this script-wise
How I would probably go about this is to have two arms (client side!), maybe sourced from the player’s model, I have no idea, and have them no-collide and be invisible when it finds that you’re out of first person, and don’t do anything to them. But then, when you’re IN first person, make it so the two arms snap into reality and start moving around with some animation you gave it.

P.S: if you don’t know how to script please learn since I’m not the guy to give you the scripts to this. I had already mentioned I have no idea how to go about this in scripting, haven’t I?