Heimerdinger's Turrets Track Ghosts

I have no video or picture but I saw Heimerdinger place down a turret in baron river near mid lane bush. It was literally shooting at nothing, doing no damage what so ever, but it was clearly shooting at something. Also, you know how Heimerdinger's turrets kinda shrink and disable when hes away from them? Well he was away from that turret and it shrunk but the barrel of the turret was still doing a shooting motion as if it was still shooting at something. I don't think this part matters but he was using the Snowmerdinger skin. What's going on?