Halo Flood 41

The commandos were up on the first level by then,
just approaching a door to the outside, when one of
three waiting Marines saw a glint of Covenant armor
within the alcove in which he was hiding, and opened fire. There was complete pandemonium as the humans ran through clip after clip of ammunition, Grunts were blown off their feet, Elites fired in every direction, and soon started to fall.-Chpt.8 pg.243