I say let him have his Cake-Lite and let him Lite-Eat it too.
Technically the party has to use and succeed
on the right Knowledge check, to have any
idea about what monsters they face. Then the
Know check dude has to free action say what
monster is what. And the rest of the party has
to hear it too ... (Listen check).
Pally Jr has to succeed his Sense Motive check
to make sure know dude wasn't fibbing.
So the party killed 6 Orcs. Doofus killed 1 or 2 of them.
Did he kill the level 8 Chieftain ... or the level 1 "Cheef"-tain ?
Kinda like queen amidala and her fake. He doesn't know.
The know check guy doesn't have to tell him. Nor the DM.
Just make sure he doesn't look at the dead, but
slinkyOrcess ; because you know what he was just thinking
violates his Paladin's code.