Involuntary Euthanasia Achievement
Kill the 2 soldiers before the building falls on them in Uprising
During the mission "Uprising", you will come across a bus where you will get ambushed. Dispatch of the enemies here and come out the other side of the bus. As you step forward, the building in front of you on your left will become unstable and start to collapse. Quickly shoot the 2 enemies standing underneath (sometimes only 1 will be there) before the building crushes them.
Alternate method: Throw a grenade from the bus to kill the 2 guys.