I read something a while back about people with 'suicidal tendencies'. At least according to the article, it is quite common that when someone becomes suicidal, they do not consider the consequences of their action on other people. It's not that they don't care that other people may die, the thought that they could be killing other people never even occurs to them. Hence the person who turns their car into oncoming traffic never even thinks about the possibility that people in the car they collide with may be seriously hurt or killed.
Rather scary if true, but it would help explain things.