Heyyo,
Yes, outlett's are fatal if across the heart. That's the thing, he probably only gotta finger or arm shock. If he stuck key's in each hole then yes he'd probably die.
Now, with this 9 volt? maybe. It thought their ampere's were only 1mA? ??? anywho, ya never know I guess.. I heard of a guy dying from a 12V car battery, then again his hands were bloody, so yeah, probably the case with blood having next to nothing resistance so all the force goes straight through the heart..