When this creature dies, it deals 3 damage divided as you choose among one, two, or three targets.
You divide the damage as you put Gang of Devils’s triggered ability on the stack, not as it resolves. Each target must be assigned at least 1 damage. (In other words, as you put the ability on the stack, you choose whether to have it deal 3 damage to a single target, 2 damage to one target and 1 damage to another target, or 1 damage to each of three targets.)