Facebook – Finding all picture uploads by a certain user, to a Facebook group

There's a lot of promising young artists posting in Facebook groups who don't have proper portfolios yet. And I need to hire an artist or three.

But first I need to do my homework! I have to check out enough of an artist's pictures to know that the one I loved is representative of their work, and not a fluke. Doing a basic group-search by username fails: Many of these groups get enough traffic, and more of these posters comment on other posts that searching on their name returns mostly other people's pictures.

For example: Search the group "Daily Spitpaint" for posts by "Tomislav Jagnjić" today, and it only pulls back one picture by him. I know that's wrong: I've found more posts in other groups linking back to Tomislav's pics pictures in the "Daily Spitpaint" group.

Which brings me back to the question: How do I find all picture uploads by a given user in a given group?