So I decided to look into this a little bit because I heard people saying locally that the weapon was NOT registered. Yet I found no stories online listing any gun related charges. Is it possible that these charges are just related to the video itself and the gun charges are considered to be part of the arrest so that he can be charged separately because there is no double jeopardy? Not sure what to think, but I suspected someone this stupid did not have a registered fire arm.
This story explains the charges a little more clearly.

So a child was operating the camera, corruption of a minor will stick.

They are also claiming that since the video names the Philadelphia Police department specifically, that is why the terrorist threat charge was added on top
of the harassment charge.

He also has a previous record, I doubt anyone will be swinging the bat for this guy , he will likely get the opportunity to plead down and out of the aggravated assault and perhaps one of the two verbal charges.