As he's at least partially surprised, go for a -4 penalty to hit an arm or leg, -2 to hit him in the chest, keeping in mind he's got armour there, or -6 to hit him in the head.<br/>If you also want to hit someone else, too, the penalty is a further -3 for the same areas, because they're easier targets, being fully surprised, but you get a -5 for a second action ;).<br/>I also remind you of your Aspects, and if you decide to use them to re-roll, you can pick a different target altogether.