They thought they had the bomb covered. No way the other team could get to it. They didn’t count on flying ninja squirrel soldiers, of course. No one expects a flying ninja squirrel.
All you really have to know to understand this play (via MLG) by Call of Duty pro Jared “Nagafen” Harrell is that he’s is the last man standing on his team, and he needs to defuse a bomb to win the round. The other team thinks they’ve got the bomb locked down. No chance he’ll reach it. Just cover that door, right? Don’t let anyone through that door!
Oh… shit… uh, maybe watch the trees, too. And maybe look out for the guy who’s literally standing right next to you.