I'm stuck in the departement of Justice I clear the NPC then found the ammo box that need a key ( true sons key ) that I cant find I look every ware I when down in front of the 2 garage door on the other side there's a door where I see the icon that point behind but got no interact on the door and I look every ware. ?????????? I maybe miss something but cant find what. I did all the other mission also went to the DZ.

Can someone hep me on this. Please

Thanks