Game-play bug with Heimerdinger turrets.

I'm not 100% sure of how it happened, but I'll give it a shot. I placed one turret up top just past their first lane turret. I went further up lane, as i was back dooring. I saw a wild Leona and placed my remaining two turrets ready for a fight. They fired upon her, but she was too tanky. i backed off and she killed those two turrets. I, however; still noticed bullets hitting her just not doing any damage. I walked back to my first turret and it was nonstop firing into the fog of war telling me the exact location of the wild Leona. My teammates noticed it as well and it was all and all a weird experience. I didn't try to do it again but as i said i have no idea how it happened.