You took control of the creature, you did NOT take control of the equipment. It is the equipment's ability that triggers, which is controlled by your opponent. So the ability makes the equipped creature deal damage to your opponent's opponent, which is you.
You took control of the creature, you did NOT take control of the equipment. It is the equipment's ability that triggers, which is controlled by your opponent. So the ability makes the equipped creature deal damage to your opponent's opponent, which is you.