Consider the following situation. The PCs are going along a road when they meet some NPC bandits. At first there is just tense negotiations, but no actual combat, until at one point in the negotiations Bob, the party's ranger, says he wants to shoot his bow at one of the bandits. What happens?
- Do you have everyone roll initiative, and Bob doesn't get to resolve his attack until his turn comes up in the initiative order?
- If so, and the bandits roll highest on initiative, then what do the bandits know on their first turn? Do they know that Bob is about to shoot, or that some PC is about to do something? Or as far as they're concerned, nothing unusual has happened yet, so they will probably just keep talking?
- Or do you resolve Bob's shot first, pre-initiative, and then roll initiative and go in order? (So Bob could potentially get two shots in a row if he also rolls highest on initiative - both his "pre-initiative" shot and his regular shot?
- If Bob can act "pre-initiative" in this way, does he get a whole round's worth of actions "pre-initiative", or just one action?
The surprise rules in the PHB don't seem to cover this type of situation. The surprise rules seem to cover e.g. ambush situations where one side doesn't see the other; in this case, both sides clearly see each other and are aware that a fight could potentially break out. (Would the result be different if both sides saw each other but one of them wasn't aware that a fight could be imminent? For instance, rather than tense negotiations with bandits, let's say that the PC and NPC were sitting next to each other in a tavern, and all of a sudden the PC just decides to take a swing at the NPC.)