Which mechanic, when?

Hello.

I'm interested in how people would turn the following action into rolls/moves.

Two PC's decide to shoot at each other.

Is it that they're both going Aggro, and interfering? So - both roll to interfere, then roll the modified by that Going Aggro?

Or is it that I decide one of them goes first, they Go Aggro and the other is Under Fire?

It might be either of those.

They might both be seizing by force.

They might not be making moves at all. You can just choose for them to exchange harm for harm.

Wow, fast!

That's very useful  -I was thinking I needed to work out which one specific combination of moves it was - but the problem was I could see it being done in so many ways.

If it's dependant on the circumstances and the narrative instead then I'll just go with what seems right and the players agree at the time.

Thank you. (c:

Perfect!