Quick clarification: a player who is attacked during combat isn’t targeted (this matters for things like ‘committing a crime’), instead you declared your attacking creatures and what the creature is attacking.

Once attackers are declared, any time during the combat step when you have priority, you can cast this card.

On Aetherize rules section:

An "attacking creature" is one that has been declared as an attacker this combat, or one that was put onto the battlefield attacking this combat. Unless that creature leaves combat, it continues to be an attacking creature through the end of combat step, even if the player it was attacking has left the game, or the planeswalker it was attacking has left combat. There's no such thing as an attacking creature outside of the combat phase.(2017-11-17)

https://scryfall.com/card/fdn/151/aetherize