Welp. GREG will be near the bridge collapse so he can save Snape's arse. I'd say he dropped somewhere around the bridge sometime the night before and just passed out, since he's been fighting and patrolling nonstop for like 48 hours. Seeing Snape get hurt will shift him back into gear, though.
He's pretty aware at this point that everyone in that village means something to someone, except him. So he's been focused on helping whoever he can without much regard for himself. Repaying bad old karmic debts, or whatever. :) He'll keep that up today, moving around huge hauls of supplies or helping hurt stragglers however he can.