Typical next steps...
--Maybe call about rehab. Or will claim he did. Decide it's too expensive/can't take time off work, will do it on his own. Drinks again.
--Go to an AA meeting or two. Decide it's not for him, will do it on his own. Drinks again.
--Decide it was all a one-off and he can control it from now on, but he still wants to drink "socially." Drinks again. Not socially.
--He's under a lot of stress, he wants a drink, stop trying to control him. Drinks again.
--In short, he will drink again and blame everything and everybody (including you) but himself.
I'm not trying to be your worst nightmare. There are alcoholics who get sober and stay sober after an incident like this. I'm currently on day 626 sober using only this board. But it was the people on this board who helped me really understand that there is no external event that puts alcohol into my body...it's ALWAYS my choice.
Until your guy gets that...and honestly, sneaking an entire fifth of whiskey in less than an hour and passing out is pretty late stage behavior...nothing will change.
I'm harping on the doom scenarios because you are so new to this relationship...you can get out early, before all of this becomes normalized and you get so enmeshed that it gets harder and harder to get out. It's like quicksand.
This won't get better. Know that and then decide if this is how you want to spend your one precious life, yes?
Sending you a hug.