The loneliest character in The Heart Is a Lonely Hunter

It's no surprise that Carson McCullers's The Heart is a Lonely Hunter ends with darkness and sorrow - the whole tone of the novel is of sadness, of people with lofty ambitions who are isolated from one another, prey to their character flaws and addictions and obsessions, and trapped in the dismal poverty that affected all but especially the black population in the mill towns across the U.S., in the 1930s and still. At the end, all of the major characters are alone and frustrated by their failures - with the possible exception of the teenage girl, Mick, whom we believe will move, somehow, beyond the confines of her family and her community - that is, we sense that she is a stand-in for McCullers herself and will tell this tale, in some manner. (We have to assume at the end that she's not pregnant; we never learn the fate of her next-door neighbor, Jimmy, who ran away after he and Mick had sex.) What does come as a surprise - possible spoilers here if you haven't read the novel yet - is the death of Mr. Singer, the man who is deaf and who is at the center of the novel: All of the other main characters tell him their stories, their hopes, their aspirations, and of course he says little to any of them - his hopes and dreams remain his own secret. We readers, however, see that the others do not - his deep love for the "best friend," Antonopoulos, another man his is deaf and mute and confined to a mental institution about 200 miles away. Though McCullers is never explicit about this, it should be apparent to most readers that Singer is in love with his "friend," and their relationship in a way mirrors the relationship between Singer and the others in the novel: Singer communicates to A., who says very little and in fact doesn't seem at all interested in Singer or his affections. At the end of section 2, Singer takes a long vacation and plans to spend a week visiting with A., but when he arrives at the institution he learns that A. has died. Singer returns to his home in the boarding house and shoots himself. This shocks everyone but us; why did he do it? First, his friendship w/ A. is seen, at least he sees it, as homoerotic love - and he also sees A. as the one person to whom and w/ whom he can truly communicate his own thoughts and feelings. (The other characters aren't especially interested in what's on S's mind.) Second, A's death was a complete surprise to Singer - maybe it shouldn't have been, as in his previous visit A had been in the medical clinic, and he has not heard from A for several months.  A's death, thought, is an ultimate rejection of Singer; we would expect that A. might have left instructions to communicate w/ Singer or even include Singer in his will (we learn at the end that Singer had left his meager estate to A.); or, at the very least, Singer's cousin, who runs the fruit and candy store in town, should have communicated something to Singer. The complete failure to include Singer w/in this sphere of knowledge is a final and bitter rejection - he is as much an outsider as any of the other characters, the loneliest one of them all.