In Ender's Game, how can Ender kill without knowing it?

[Springtime]

I just finished reading Ender's Game and haven't yet read any of the other books. There was something I thought was odd about Ender killing Stilson and Bonzo. Ender feels remorse and does not want to be like Peter, but how can he kill those other kids and not even know it? The teachers make sure to hide the fact from him, and he tells himself he hurts them bad enough so they'll leave him alone afterwards. He's supposed to be a genius though, so it seems like something he wouldn't be able to overlook. Or is it that he knows this fact all along and just doesn't want to admit it to himself so he sort of blocks it out?

[neo-dragon]

It's certainly possible that Ender was aware on a subconscious level, but on the other hand, why should he have known? It's not like he had an opportunity to check their vitals. Even doctors and paramedics can't confirm someone as dead at a glance unless there's something obvious like their head laying several feet away, and it's certainly not reasonable to say that he should have known that he was inflicting lethal damage.

[Springtime]

Hmmm....that's a good point, I never thought of that. I was thinking it'd be easy to tell a person was dead, but I guess you're right that it probably wouldn't be as obvious as I first thought.

[StrivingForSatyagraha]

It would be even harder to notice if you were being fatal if your intention was not to do so in the first place. Ender did not want to kill Bonzo or Stilson, he just wanted to finish the fight thoroughly, by hurting them so bad that they would be afraid to come back at him with other, it just so happens that he finished it thoroughly enough that it was fatal.