To get by them, don't go through the door they are right behind, but stay outside that door and look left. There is a crate there, go jump on it and jump straight up to the landing. You can go in the side door where there is nobody else.......yet!
I've cleared the chests/barrels on that level and the next one up. Found some good weapons in there.
You can do so only to just collect the chest earlier, but cant venture up to meet william, since he will auto had a conversation with you once spotted you and the quest will be trigger. You can actually skip it and keep them for later since there are freaking lot good chests in the whole broken valley. But once you starts fjords and able to purchase legendary gear directly from merchants, I bet you wont bother much of chest's contains anymore.
