How do I connect gun, hand models to anim and camera

I have a basic soldier model in a T-Pose, it has its hands in the graphics section, but there is also a gun included into the Main Camera of the Empty GameObject of the soldier model.

the gun is following the camera, but the hands stay in a T-Pose. how can I connect the arms to hold the gun(rifle) and also follow it without being a part of the camera. and also making animations apply to both of them.

Thank you.