The suicide suggestion was raised but discounted fairly quickly. And I'd think on something like that we can rely on what we are told being the truth, since suicide would surely have been a more satisfactory way for them to die from the point of view of the occupiers.

In a siege situation like that, there should not have been any need to "look down the barrel of an AK4". Not unless for some reason they needed to storm the building, and there wasn't any such need. Maybe sooner or later the brothers might even have decided to kill themselves, in which case, why do the job for them?