Imo, the entire "you must go non-lethal at first" can be kinda bullcrap. In real life situations, if a weapon is drawn the cop is gonna go lethal. It is Roleplay and should be somewhat realistic to being an IRL Police Officer.
I don't think he should receive a two week for it, if anything reduce it to one week for Unintentional Mass RDM but I believe it's just a lesson learned.