This guide explains where to find the symbols from beneath hidden in each scenario.
The biker bar symbols are hidden in the staff room behind a shelf full of boxes.
Once you enter the staff room find the shelf full of boxes, move the ones on the bottom shelf And there it is, hidden behind the boxes.
So, the symbols in club beatdown are a little easier to find. You have to go up the stairs and kill the katana boss and his goons. The symbols are cleverly hidden on the back of the chair.
The symbols hidden in prison are found in the solitary row of cells. This is where the big guy is locked away. Once you get to the solitary cells you have to press one of the buttons to open them up and then enter the cell to the right of the giant prisoner.
Once your in the cell look up and it's right above the doorway.
Once you've spawned in you wanna look to the right till you find a bunch of large rocks in the water.
To find the symbols you have to jump across the rocks ignoring the really tall one and you'll come across a cultist carving the symbols into the side of a cliff.
The saloons symbols are very easy to find. All you have to do is go to the fireplace and crouch-jump into it. Once inside of it quickly face the entrance to the fireplace and you'll see it above the opening.
One thing I noticed about the symbols is that they glow increasingly red the more people you kill.