The mechanics of the game will be used to determine what a storyteller would do. If they are going to make it close to the PnP as possible, then the mechanics will follow the rules of the book.
In the book, Vampires don't tolerate the breaking/potential exposure of the Masquerade. Nor do they tolerate those willing to sacrifice their humanity.
Now this is the tricky part. They can use the NPC's to follow the guide lines outlined in the PnP and if you break the rules..then you must pay for it.
But if there are already players who rule the Clan or even have a Prince in charge of the city, then perhaps the mechanics will opt to allow those in charge to decide what to do with you.
There won't be a Storyteller for each player. Each player will have to obey the rules of the game outlined by the game's rules (presumably the same rules in the book) and if the major rules get broken, then it's the players fault if they die.
If NPC's see you kill someone..or everyone, then chances are the game will do what a good storyteller would do anyway, and let you try and get out of the situation (be it kill your way out, plead to the Prince, get arrested) or suffer the consequences.
If they include Hunters in the game (even as NPC's), and they find you committing a crime..or even find you at all they wouldn't hesitate for a second on killing you, and if you stand your ground with one and fail, the outcome will be the same in the game as it would be in the PnP...perma death.
Only a soft forgiving Storyteller would let a Vampire live who goes against a higher level Hunter