I am...not entirely sure. I've not worked with him for any extensive period of time, but there have been fears of him assuming the identities of any one of the staff members if they allow close contact without safeguards. This has not—to my knowledge—been the case however.

He has not been successful in assuming staff member identities, nor those he has not killed. It would seem that he either chooses not to when the individual in question has not fallen by his hand or he cannot do so.

It may be that he is simply covering his own bases so to speak, as if he were to leave a victim alive and still assume their identity who is to say he wouldn't be named immediately as an impostor? It's difficult to say exactly. Pure speculation on my part.