The discovery was made in a second-floor apartment on the 200 block of South 13th Street.
Officials say neighbors had been complaining of a foul odor since last Friday.
The landlord returned to investigate this morning and made the discovery.
"If you smelled it, you knew it was something there; it's not right," neighbor Sandy Cottrell said.
The stench of death drifted through the neighborhood as police removed the body of the victim Monday afternoon.
The 41-year-old man was found slumped over in a living room chair.
He had been shot several times and his head was bashed in.
Police believe the killer used a fire extinguisher that was found bloody and dented hanging on the wall.
They also found several shell casings and a slug.
The killer placed three fans around the body, apparently trying to keep it cool.
Sources tell Action News that late last week, police arrested the woman who rents the apartment on a weapons charge.
She allegedly had an illegal .9mm handgun.
That's the same caliber as the bullet and shell casings found at the murder scene.
Police are still trying to verify the identity of the victim.
He had a California I.D. in his pocket.
The woman who lives in the apartment just moved in a month ago and neighbors told police they didn't hear any loud arguments or gunshots.
Sources say when the woman who lives at the apartment was arrested, she told police her son was threatening to commit suicide.
The police had nothing to go on then, but when they returned today because of the bad odor, they found a murder victim, not her son.
Detectives are continuing to question the woman.