One, figure that the aspects of "Point Blank Range" and "In my sights" are applied. Thats +4 right there, a weapon 2 and a Fair +2 gun skill. With the best roll possible, your looking at a possible 10 shifts plus a weapon 2. So if Harry rolls bad, he's getting approx 8 shifts of damage, thats going to hurt a mortal any day of the week.
Also, Harry doesn't know how many stress boxes he has.
Thanks for the replies. The game system is a bit different, compared to "traditional" RPG's (read: that are trying to simulate reality more than the FATE-system does), so it takes some time getting used to a different mindset.