Your first target leads you to more.

Daily   ✦     Martial, Weapon
Standard Action      Ranged weapon

Target: One creature

Attack: Dexterity vs. AC

Hit: 3[W] + Dexterity modifier damage.

Miss: Half damage.

Effect: Until the end of the encounter, whenever the target moves adjacent to another enemy, you can make a ranged basic attack with a weapon against that enemy as an immediate reaction.

Published in Dragon Magazine 383, page(s) 50.