They do not appear to be from the same unit in any close sense. All three soldiers, as with most soldiers at Fort Hood, were assigned to III Corps. As an Army Corps is a unit (a very, very large one with 60,000(+) soldiers counting all soldiers, at all bases), some reports may of stated that all three were all assigned to the same "unit". This is technically correct, but not correct in the practical sense. Two of the soldiers were assigned to the 1st Cavalry Division (about 15,000 soldiers), but to different brigades and thus to different battalions. Though some may consider assignment to the same Brigade (non were) as being in the "same unit", I think most soldiers would use the term "same unit" to mean battalion or smaller. Thus, for the three soldiers to have been assigned to the same unit in the practical sense, I think they would needed to have been assigned to at least the same battalion (about 800 soldiers). None were.