It's a more earnest answer than Joan was expecting. That, more than anything, unsettles her. The idea of him as a person, giving her an honest answer and not more bottom line bullshit- well. She doesn't know what to do with it.

She keeps watching him out of the corner of her eye.

"How'd it happen?" She doesn't think she'll get a real answer, but she's curious to know what he'll do when he's asked so directly. Probably hit her. The last time that happened while she was driving a car, the world hadn't ended. The more things change...