Can I use CSS to order by row but align by column?

Question

I have a 3 column layout that I want to order left to right, but I can't find a way to keep images from starting below the largest image in the row above them. Is this possible with only CSS?

To be specific I want to order my objects like this:

http://codepen.io/lorenshumaker/pen/PZebjm

ul {
  display: flex;
  flex-direction: row;
  flex-wrap: wrap;
}

but I want them to align like this:

http://codepen.io/lorenshumaker/pen/gPzLGW

ul {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
}