Heimerdinger Turret Firing across the map

Heimer set down three turrets in the brush closest to river between blue and outer, mid, red turret. Tristana jumped over the wall from blue and was targeted by the turrets. She walked away and one turret continued to shoot her even though she was out of range (she went all the way to tier one mid turret and then down to bot lane tri-brush) and it was still hitting her and actually causing damage. I have only seen this occur one other time (can't recall the specifics).