Doomsday Mural/Union Depository - Skeleton Key Button Found on Elevator Panel!
I was playing Franklin and Lamar and picked up sticky bombs from the house under construction along the way. Now normally when I enter the Union Depository following close to Lamar there is a Gruppe 6 security guard standing at the garage entrance who Chases after Franklin, a Gruppe 6 armored truck parked in the loading bay and the Loading Bay Door Locked so I failed the mission and tried it again but decided to stop before exiting the Arcadius parking garage, letting Lamar drive through the Union Depository by himself. I jumped out of the car and ran towards the security guard and noticed he did not recognize me which I thought was weird. So I jumped back in the vehicle put the top up for safe measure and proceeded to enter the Union Depository without the Gruppe 6 guard giving chase. When I entered the loading bay I noticed that the Gruppe 6 armored truck was gone and the loading bay door was open Loading Bay Unlocked Door I went inside to investigate the interior and was able to kick open the doors of the Elevator used to transport the gold from the safe to the armored trucks. Being an elevator the only thing of interest is usually the Elevator Button Panel that cannot be seen in the cut scenes of the Big Score. The button panel has a few buttons on it but if you look at the bottom button it's the picture of a Key Now the keyhole from the Union Depository Logo can be found on the Purple Doomsday Mural so maybe it's the key to that hole and the key to the mystery or maybe it has something to do with the Big Score mission itself. When the armored truck is destroyed the first stack of money I pick up is $10 unless I picked up 2 stacks at the same time, beyond that each stack of money is $5 and I pick up a total of $192. To obtain the money from the armored truck throw 3 sticky bombs where I did and look for the oil leaking on the ground and throw another sticky bomb at that, enjoy!