First you set them up, and then you knock them down.

Encounter   ✦     Martial, Weapon
Standard Action      Melee or Ranged weapon

Requirement: You must be wielding a crossbow, a light blade, or a sling.

Target: One creature

Attack: Dexterity vs. Fortitude

Hit: 3[W] + Dexterity modifier damage. If the target hits or misses you with an attack before the start of your next turn, you can repeat the attack against it as an immediate interrupt, dealing 2[W] + Dexterity modifier damage on a hit.

  Brutal Scoundrel: You gain a bonus to the attack roll of the immediate interrupt. The bonus equals your Strength modifier.

Update (10/3/2011)
Updated in Class Compendium.

Published in Player's Handbook, page(s) 124, Class Compendium.