Cat growls and hisses when chewing paper

Our 1 1/3 year old cat loves paper .. he is always able to find a piece around the house.

Then he chews it and while holding it in his mouth he growls and hisses.

No other weird behavior.. he's nor mad or upset when he does this .. I can go take the paper .. no problem - or pet him and he is in no way upset..

We do have another cat in the house (his mom) .. yet she is not near him [but in the same or next room] when this happens.

He is otherwise a really affectionate, playful and happy  cat ..

He just started with the growling and has never done it before under any circumstances.

His teeth are ok and ... and he's not in pain or anything..

Any ideas?  It's a liittle scary the sounds he makes.. -- like a wild animal.

I think it's his unique way of showing his enjoyment with the paper. 

thanks you - - we hope so 

Our youngest does that as well, but with plushies instead of paper. She puts them in her little mouth and hide somewhere, while hissing and growling at it constantly, but she would never attack us or act aggressively if we tried to take them away.

Apparently it's a bit of the cat's hunting instinct that's surfacing. But as long as there's no aggression towards you or any of the other housemates, it's all just fun and games.

They're still cute little furry Hannibal Lecters, after all