How to destroy all enemies within X distance after picking up destroy power up by pressing L key?

Hi

New to unreal looking for how to set up something up.

Have a top down built from scratch. Would like to have a Boolean variable called powerup become true when I run through a power up sphere. If I press the attack key, L, I would like all enemies within X distance, a variable I would like to be able change as character levels up, to be destroyed. When the attack key is pressed I want the power up boolean to be set to false. Will need the enemies tracking how far they are from the player.

Could anyone guide me on how to set this up?

Thanks