I was getting killed regularly during a game while standing on that same balcony. After dying twice i seen where the dude was and blasted em.

If you look straight out from the balcony across the courtyard to where the player spawn point is....the building to the right its possible to get up on the roof. Since the roof is slanted you'll only see a little bit of the dudes head sticking up when looking from the point you were shot at.

After shooting this guy i went into spectate mode figuring he'd try to get back up there and i'd see how to do it. He went into the second floor of the building, out on the little balcony, he then jumped up on the railing..You'll notice theres a telephone wire coming from a pole in the courtyard to that roof thats very close to the balcony. He was trying to jump off the balcony on to the wire. Once on the wire walk along it to the roof.
Hope i explained that alright. anyhoo just look for the pole and wire.
The dude never did make it to the wire.
I watched him try it about 3 times. After this i went on a server running the same map with noone on the server and tried many times to do it, no luck.
That could explain you getting shot with no one around.