I've seen the full pic. The wall behind him has quite a few such pix of guns, all pointed in the same direction. But:
* AP's photog took the pic from that side, not a back corner, the other side, or face on;
* Public speakers typically turn their heads to sweep the audience to who they are speaking;
* AP's photog took the pic from the precise position that put the gun barrel close to Cruz's face and pointing at his eyes.
A particular side of the room, a particular angle from that side, Cruz's face in profile rather than at an angle, a gun right in Cruz's face, pointing at his eyes. Coincidences? Not utterly impossible, but very highly improbable.
Call it barely plausible deniability. And the sneaky MSM tricks have only started; there's 16 months more coming.