The piece says that they attempted to attack the safe room and could not penetrate it. So they had to know that it was a refuge and somebody was there. Hence, the conclusion that such a redoubt might not house the ambassador would be illogical. The shape of the hallway would have precluded the effectiveness of all but a gas grenade.
Actuallyt, I thought the FoxNews special said simply that they tried to get in the door but were unable to.
It says clearly that teh special agent had a gun trained towards the terrorists should he need it...but he never fired. I believe they werre hunkered in back there and that the tangos tried to break in, but were unable.
I do not think they knew the ambassador was in there or they would have either brought in something ehavier to get the door down, tossed grenades (if it were their intent to kill him), or waite dlonger for more support. As it is, they simply burned the building.
It is not clear that they knew someone was in there from this report.
An interview with that Speical Agent would clear it up. One day he or some of the others will write a book...which I will most cetainly buy and read.