Tower glitch

I just had a game where this happened. I was tower dove by Ahri who took 2 tower hits before I died and then ulted away from the tower. However, she was still in range and he tower shot at her for a 3rd time. She had barely any health but the shot did no damage at all to her. This happened again the same game where a final shot should have killed her but didn't it. It seemed the tower (on my death) stopped doing damage to her both times.