Laboratory Sneak Kill - Secret or Bug ?

[CHALLENGER]

I don't know its a bug or any kind of secret but I kill Snake behind Blue force shield with Fireballs in Laboratory so is there any kind of secret or its just a bug ?

Actually I am targeting one of the enemy in front of Snake cage but enemy moves & My Fireball heats the snake & I saw damage points so I said what the hell & I thought its some kind of secret so I reload the last save & again go to Laboratory then I first kill all trapped enemies by clicking wrong choices & after killing all enemies I try to kill each enemy but I only got success in Snake kill & I only got 200 skill points & there is I think snake tail in cage but its not possible to grab it other than that i don't found anything related to it so please can one tell me its a bug or secret ?

[Vardis]

It's a bug.

[CHALLENGER]

Ohhh Sad, I waste lots of time there btw Thanks.