As he moves to kick her, several things happen at once. First, the grenade explodes, though, fortunately, she was bluffing, as the room very quickly begins to fill with smoke, not explosive shrapnel. While his kick does connect, she seems to have been prepared for it, and, while she hits the ground hard, he can hear her rolling away into the blinding smoke. Third, moments later, the minigun opens up, spewing a brief hail of bullets in the general area of where he's standing.