Nunu Ult Double Kill On One Person

I don't have any proof but this happened in a game yesterday to me. I was getting banked by the enemy as an ap nunu, against another ap nunu in lane. (TY instalok) and we both ulted. It said we both got double kills and it showed him killing me twice on the side. I got 2 deaths extra and he got 2 kills. Was a normals so didn't really matter and I was cracking up for like 10 minutes but this really should get looked into.