Secure the plaza

Secure the plaza

I have tried getting past this level several times now, but it seams I am stuck in the plaza area.
After I enter the back of the building (thru the alley), I shoot the red gas tank and kill the sentry standing next to it. I then tuck into the left corner of the doorway (before) going into the main room with reception desk. I pic off 11 or 12 other soldiers as they start to walk through the doorway. I then move to the third floor on the opposite side of the building and take out 4 snipers in the buildings around the courtyard. I then move to the building on the right, enter and take out 2 additional soldiers. At this point there is no one else to shoot, but I cannot get to the next level, or to the street beyound the street rubble at the far right corner of the courtyard. What do you have to do to get through this level?