Multiple Monster Hit Question

[pitfal]

This just came up in our game. Friend had 3/4 health. He ended up in a room with four different monsters and could not win. He has several healing potions. Here is the question; Do the hits from these four monsters happen at the same time killing him immediately, or do they happen one at a time allowing him to use a health potion to save his life?

He was clearly in the in the lead when this happened and the table made the decision that it would insta kill him. He argued that he could heal out of this situation. Anyone have an official answer on this?

The mood changed quite a bit with this decision.

Thank you in advance.