Probably someone screwed the ladder into the wall and one of the screws hit a wire inside the wall or if the building wires are in metal conduit pipes, sometimes they get pulled or bent and the wires can come into contact with the metal pipes - especially at junction boxes where the insulation has been taken off for connection to switches etc. I've seen a lot of that kind of stuff in industrial spaces where fork lifts and shelving are present for example.
That's just a guess but perhaps its a good idea for you to keep your shoes until you find out the source of the power - maybe even wear rubber boots and gloves?
You can track the source down by starting to eliminate things one at a time - pull the laptop charger off the computer, use a different monitor, different tether cable, or switch off one fuse at a time in the buildings electrical breaker box. When the shocks stop, you know at least what part it was coming from.
