Parenting game object to bone change bone pivot point

basically i have rigged hands model in blender and exported them to unity and everything was working fine with the model, the bones where moving the hands as they should. i wanted to make an animation with a gun in the hand of the model so i parented the gun to the hand bone, that way it will look like its holding the gun, but when i start animating, the bones above the hand bone (upper arm, lower arm etc) rotate around the gun instead of rotating around their pivot point, is there a fix to it or do i have to make the animations in blender? btw if i make the animation without the gun and then parent the gun at runtime it works as expected

found a kind of answer using a constraint component