Razing buildings

I recently played my first terror mission and on the edge of the map there were two apartment buildings. My highest ranking soldier was searching the building when it suddenly collapsed completely, killing her. I think there was a shot but I'm not sure, there definitively was not any explosion or anything. The building looked completely intact when she entered, no visible damage at all.

Can the aliens really completely level a building with a plasma rifle? Is this some special terror site deal or what? After the building collapsed I noticed that another had collapsed before my soldiers got there.(so there was a total of 3 apartment building on the map) I initially thought it was a graphics glitch as it didn't look like rubble. Is that a sign you need to take extra caution or do I have to avoid buildings all the time now?

Buildings can be demolished by destroying walls, although the amount of damage needed seems to vary, and some of it is definately buggy. Once sufficent walls (on the ground floor I think) have been destroyed, the whole thing collapses.

Buildings can be demolished by destroying walls, although the amount of damage needed seems to vary, and some of it is definately buggy. Once sufficent walls (on the ground floor I think) have been destroyed, the whole thing collapses.

Do you know whether the soldier is guaranteed to die, whether under or on the building?