Sagittars' Volley — ruling 1

If the target creature is an illegal target by the time Sagittars’ Volley tries to resolve, the spell doesn’t resolve. No creatures are dealt damage. If the target is legal but not destroyed (most likely because it has indestructible), creatures with flying your opponents control are dealt damage, possibly including the target creature.

Sagittars' Volley — ruling 2

Each creature with flying controlled by any of your opponents is dealt damage, even if that opponent didn’t control the target creature with flying.

Sagittars' Volley : règles, fonctionnement et interactions (MTG)

Sagittars' Volley is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Destroy target creature with flying. Sagittars' Volley deals 1 damage to each creature with flying your opponents control.

How it works : Sagittars' Volley

Original English text — Wizards of the Coast / Scryfall

#1January 25, 2019· Wizards of the Coast
If the target creature is an illegal target by the time Sagittars’ Volley tries to resolve, the spell doesn’t resolve. No creatures are dealt damage. If the target is legal but not destroyed (most likely because it has indestructible), creatures with flying your opponents control are dealt damage, possibly including the target creature.
No other card is named in this ruling.
#2January 25, 2019· Wizards of the Coast
Each creature with flying controlled by any of your opponents is dealt damage, even if that opponent didn’t control the target creature with flying.
No other card is named in this ruling.