testlum says:
This means that only Jacky's 2nd shot runs the risk of hitting an ally for round 1, right?
What counts as melee here? If on round 2, Jacky shoots at one of the halflings on the back rank, does the arrow still have a chance of striking an ally?
Sorry, I could have been clearer in my previous post; I will go back and update it.
In round 1, Jacky, Grim and Thrud, as Fighters with multiple attacks, all perform their attacks at the same point in the round. Jacky is shooting, and Grim and Thrud are meleeing following their charges. Therefore, Jacky has a chance, with his first shot, of hitting Grim or Thrud.
By the time of Jacky's second shot, Zach will also have joined the melee. So he becomes another potential target alongside Grim, Thrud and the halflings.
If you are within 10' of an opponent, you are generally considered to be in melee.
I'm not going to insist you shoot. You may hold your fire if you don't want to take the risk. But that will still remain your action for the round.