What should a mourner do when greeted with Shalom

A mourner after three days, when people come to comfort him and greet him with Shalom, knowing he is in mourning, should he respond with Shalom?

A mourner after the first three days responds with Shalom in a soft voice, and only if the person who greeted him did not know he was in mourning, or knew he was in mourning but did not know that it is forbidden to say Shalom to a mourner. However, if he knew he was in mourning and knew that it is forbidden to say Shalom to a mourner, and still said it, he does not respond.

Mordechai writes at the end of Tractate Moed Katan: "From the third to the seventh day, he responds to those who do not know of his mourning, but does not inquire." Similarly, it is written in the Shulchan Aruch, Siman שפה: "If others did not know he was in mourning and inquired about his well-being, he responds to them." This implies only if they did not know he was in mourning. However, as the poskim write, in Siman תקנ"ד regarding Tisha B'Av, it is established that one responds to commoners even if they know it is Tisha B'Av. From this, it can be proven that even if he knows he is in mourning, but does not know that it is forbidden to say Shalom to a mourner, the mourner responds to them after three days.