Chassidim are like one family; the Rebbe is the father of all Chassidim, and Chassidim are his children (and this relationship exists all the more with the Shluchim, with whom the Rebbe has an extra close and personal relationship).
Thus, the Rebbe is sitting shivah now, and all Chassidim should be sitting shivah now.* So to all Chassidim, and to the Rebbe, I say:
“Ha’mokom yenacheim eschem besoich shaiar avelei tziyon ve’Yerushalayim.”
*Just to clarify for those inclined to interpret things too literally, I mean that in one’s heart, that is how one should feel.