I think it's Glenn. The first person shot after each commercial break shows us a perspective from someone who had already been captured and we have the same perspective of that person dying.
Also, Maggie cut her hair in the episode before. Cutting hair in the Walking Dead means something and I think for her character to change that much, Glenn has to die. I mean, they've already killed him before so they aren't doing anything new.
I know the comic has nothing to with the show but Negan kills Glenn there, which I know is something everyone thinks won't happen because it happened there. It might happen, because in the comic, what is that idiots name, leader of the hill top? Anyway, he is obsessed with Maggie and it would make an interesting twist seeing her alone with a baby. And Maggie also commits suicide in the comic, so not sure what they might do with that.