It's not a second shot. It's simply the RAW of Ulric's Fury. You make a second roll to hit with same modifiers, and if that second to hit scores, then the Ulric's Fury takes effect (and you're allowed to roll another damage die).
It's just the rule. If you fail the second to hit, it means it's a regular hit with 10 damage, for a total of 14, which is still a nice result.