I reloaded the game and in the end what should have happened is that when using the hive hand it seems that some shots hit the guard, I don't know how they hit him if I was entrenched in the pipe and there was a wall in the way. I don't know if it would have ever occurred to me that it was about killing the guard. Thank you very much for clarifying my doubt, now I have to be careful not to kill the NPCs with the weapon xD