Stuck on level???

I am over 9/10th of the way through the campaign. I am on an upper floor in a high-rise building. I need to go higher and identify a target for an air-strike.

I'm stuck, killed all the squids, there is a VTOL Gunship shooting at something on the ground, and I cant get off of this floor.

The only apparent way out is through one of several double doors. I have used up my C4, 50 CAL, Kicked/punched, pushed and pulled any lever/button I can find and no joy.

The only hole in the ceiling is over the staircase leading up to the 50 CAL. But I have not been able to jump up to it.

Any feedback will be appreciated.

Thanks