Question about xbox 360 resident evil?

Ya theres 3 different snipers but theres the first sniper is in the building where the helicopter gives u air support its in the builing by the gate. second one is one 2-3 in the locker were u find irving then the third is in 5-3 (i think) where u have to turn on the power =) and the ons change like for me it was x,x,lt+rt