Dead-Iron Sledge
Artifact — Equipment
Whenever equipped creature blocks or becomes blocked by a creature, destroy both creatures.
Equip 
(: Attach to target creature you control. Equip only as a sorcery. This card enters unattached and stays on the battlefield if the creature leaves.)
Ray Lago
Mirrodin (MRD)
• #162Rulings
Moving Dead-Iron Sledge after the ability triggers will not affect which creatures are destroyed.
(wotc • 2006-10-15)
Rulings
Moving Dead-Iron Sledge after the ability triggers will not affect which creatures are destroyed.
(wotc • 2006-10-15)