If Cullen were to lose a friend (one that turned into a behemoth) that he personally had to put down, would Cullen weep openly and unashamedly for the loss of his friend? Or would he choose to hold back his grief and mourn in private?
Depends on the context. Is he alone, or only accompanied by a very close friend? Is he surrounded by others, by not so intimate acquaintances, by strangers, by the men under his command? When does this happen, in the context of his life - is he comfortable showing vulnerability, or is he in a more reserved mental place, holding himself together for the sake of the people depending on him?
In any case, I don't see Cullen circa Inquisition breaking down in hysterics publically. I think he'd weep for a friend, of course, but discreetly, and leave the theatrics for a more private place. At the moment there would be more pressing matters -are all the enemies dead, what do we do with the body, is anyone hurt, how many did we lose, can anything be salvaged for a funeral, how do we get out of here, etc. Tears, sure, but also everything else that needs to be dealt with. Then later, in the privacy of his room, he could relax and cry as long and hard as he needed, specially if tipped over the edge of emotions by a friend showing concern. You know, like that one person in your family who manages to keep their head in place when a relative dies, who arranges the funeral, makes the calls, arranges the burial, stays completely sober and impassive through the whole affair, but when it's all over they just completely break down and sob their heart out? He strikes me as someone like that.