Let's see, it says Diabolus slams his head into the same building he charged earlier shortly before apocalypse's activation. That would be the building Shen was standing on at the time, which is next to Free's building, within Shen's jump distance. Given that Shen did fall a few storeys to extend the distance, the two would be about 50-100 feet apart.
Because of the 45 degree cone, Free would have to fire at at least a 22.5 degree angle, where straight down is considered zero degrees, in order to not hit his own building. If Diabolus is standing at the base of a building that is, let's be generous, 100 feet away, Free's skyscraper can be up to 200 feet tall for him not to hit its base. If it's taller than that, which it almost certainly is, and Free didn't adjust his angle, then yes, you just destroyed the base of the sky scraper... and probably Shen too. It's a good thing we have respawn mechanics in this RP.