xbox360 game ...trying to remember

Hi, it was a longtime ago i was playing this game on xbox 360...the main part i remember took me ages to beat the end of level boss...

You had to keep running down stairs to the area below and get rocket grenades for weapon and then run up stairs again to fire in massive boss,again i cannot quite remember boss off hand, but i do remember game had a destroyed hospital level, and i think it was the end of this level i encountered boss....it was certainly a destroyed building i was fighting from and kept running down to get more rockets from machine all the time....anyone know the game?? I would love to play it again....thanks.