Honestly, this. At least Falco is alive, and probably Reiner too.
I'm not one of those faggots who can't accept Eren just killed a bunch of civilians. I think it was set up pretty nicely, showing that Eren completely grasps the cruelty of the situation and that he has sort of forgiven Reiner, but still proceeds with the plan out of duty and (maybe, depending on how you interpret the dialogue) some personal desire.
But. I really don't see Eren killing Falco, the innocent kid who helped him, in cold blood. Sure, he brought Falco along as a hostage, but I think he wanted him away from the stage as well. Either he counted on Reiner shielding him, or he's skilled enough to do so himself. Next chapter we'll see Falco crawling out from under some temporary shelter Eren made with hardening. Screencap this, because it will happen.