In my campaign, if the to hit does hit the monster aimed at, I do nothing else except ask the player what they rolled for damage.
If it misses, I count off the number of characters/monsters in the line of fire.
Example: if there are 6 characters/monsters in the line of fire, I out loud and show the players, count off who gets what number of the d6.
Then I roll the d6 out in the open. If the original d20 result could hit the character/monster it is now going towards, the player who fired the bow/crossbow/spear toss, etc. rolls damage.
If it doesn’t hit, I RP it and say it whizzes past character so and so and just misses the monster going on behind the melee.