I'm a little torn, actually. I'm left wanting more information, but I also really like the ambiguity. Overall, I would say it depends on if there will be more to this story. If so, then ambiguity is just fine, otherwise - I want to know more, darn it! That said, I think it really depends on if you want to drive your readers crazy or not. Personally, I like torturing readers, so I would just let them wonder.

Also, I really liked this story, overall. I think it's interesting, and realistic, and not super action-packed, and much better for it.