Why did Emily murder Homer Barron in "A Rose for Emily" by William Faulkner?

Miss Emily Grierson, the protagonist, in “A Rose for Emily” by William Faulkner had not lived an easy life.  Her life was filled with loss, poverty, and loneliness.  Yet, Emily was an icon in her home town. Everyone knew Emily and had an interest in knowing about her. 

Reason 1-Father’s interference

At one time, Emily would have been called a “flower of the old south.” She had young men that were interested in her.  Emily’s father had other ideas for his daughter.  She was his companion. They went on rides together.    He did not allow her to have “beaus,” possibly because he wanted her for himself. In addition, he may have thought that none of her boyfriends were worthy of her hand in marriage.

Reason 2- Left penniless

Regardless of his reasoning, Emily’s father died when she was about thirty and left her entirely alone and penniless.  The only actual thing that he left her was the family home on which he owed taxes. Colonel Sartorius helped Emily with her taxes, but he eventually died and left her with no one in the city council to help her.

Reason 3-Loneliness

At the age of thirty, Emily, although she would have been considered to be a spinster, still had hopes for finding a man. Loneliness and desperation made Emily susceptible to a man, any man.   When Homer Barron came to town to help build the sidewalks, Emily set her sights on him.  Homer had announced that he liked men, but he apparently did not share this information with Emily. 

Reason 4-Rejection

On Sunday afternoons, Homer and Emily could be seen driving around the town.

Later we said, "Poor Emily," behind the jalousies they passed on Sunday afternnon in the glittering buggy, Miss Emily with her head high and Homer Barron wit his hat cocked and a cigar in his teeth, reins, and whip in a yellow glove. 

The town gossips thought that he was ruining her reputation. Rumors had spread that the job was finished and Homer was leaving town. When Emily bought items labeled with HB on them and some men’s clothes, the town decided that they were going to be married.  About that time, Emily bought some arsenic at the drug store. 

About that time, Homer was seen entering Emily’s house by the back door.  He was never heard from again. 

Reason 5-Never alone again

When the people came to look in Emily’s house after her death, they discovered the room with Homer’s skeleton and Emily’s strand of gray hair on the pillow next to the corpse. The people of the town already knew about the room upstairs.  Apparently, what the citizens really wanted was to see the room and all its gruesomeness.