In a way, Evan accidentally killed BOTH his parents. His accelerated aging not only made his mom go through nine months of pregnancy in a week, but he also vaporized her (and everything within THIRTY FEET) when he was born. And then when he went to go see his father as a teenager, they got in a fight (because Tanner was freaked out and refused to admit he HAD a son, because week-long pregnancies are just fucked up), and the dad fell on this spiky tool thing that was in the shop and died. At least with the dad, they bothered to make Evan completely horrified about it, though Clark and Lex (who found the body) were more worried that it just meant Evan had no donor. Which, you know, kind of makes sense, but... no sympathy for the mom just makes me mad now.