Obligation of Tearing Garments in Front of Others

When tearing garments for the passing of a father or mother, is there an obligation to tear in front of people who see, and not alone at home, and if necessary, is it mandatory post facto if one tore alone?

Indeed, when tearing garments for one's father or mother, it must be done in front of people, and post facto, if one tore alone for one's father or mother, it is not considered fulfilled. (It does not require a large crowd; it is sufficient that a few people see it)

Talmud, Tractate Moed Katan, page 22b: "Rabbi Chiya bar Abba said in the name of Rabbi Yochanan: For all the deceased, one tears from the inside; for one's father and mother, one tears from the outside." There is a disagreement among the early commentators about what "outside" and "inside" mean. According to Rashi, "inside" means in a room, and "outside" means in front of people. However, the Ri"tz Giat explains "inside" as inserting one's hand under the garment and tearing, and "outside". The Shulchan Aruch ruled according to the Rambam, who considered both explanations primary, and in Siman 340, paragraph 13, it states: For all the deceased, one may tear from the inside, not in front of people, therefore one may insert his hand inside and tear in private. But for one's father (and mother), one tears only from the outside, in front of all people. Post facto: The Or Zarua, part 2, laws of mourning, Siman 318: "Rabbi Chiya bar Abba said in the name of Rabbi Yochanan: For all the deceased, one tears from the inside, meaning it is not necessary to tear in front of people, for one's father and mother, from the outside, not from the inside, and it seems that all that the sages required, if torn otherwise, it is not considered fulfilled."