HOUSTON --A man whose headless body was found outside a vacant Houston house was fatally shot in the head before his body was dismembered, a medical examiner's office said Tuesday. Police discovered the head and an arm of Marlon Thomas, 35, Sunday evening stuffed into a trash bag under a house. A chain saw was next to the bag and the rest of his remains were buried in a debris pile in the yard next door. Police arrested Thomas' best friend, Noe Gerardo Morin, 32, and charged him Monday with murder. Court records showed he was scheduled for a court appearance Wednesday but did not list an attorney. Morin was jailed without bond. Roxanne Mena, spokeswoman for the Harris County medical examiner, said an autopsy determined Thomas' death was a homicide and the gunshot wound killed him. In a probable cause affidavit filed with the Harris County district attorney's office, the physician who performed the autopsy said the wound was in the back of Thomas' head and it appeared he was shot before he was beheaded. Neighbors reported hearing gunshots Saturday but said the sound wasn't uncommon in Houston's Fifth Ward. They did not recall the sound of a chain saw and documents in the case do not indicate whether the chain saw was used to dismember Thomas. Neighbors also described Thomas and Morin as best friends for years and speculated a dispute over money or theft of property might have led to the slaying, a suggestion supported in the affidavit filed by investigators. According to the document, a neighbor told police Morin came to him Sunday morning and asked him to fix his chain saw. When the neighbor returned the repaired tool, Morin asked the neighbor if he could trust him, then took him to the property next door and told him to look through a hole in the fence. The neighbor "looked through the hole and saw the body of a headless black male and (Morin) said that the body was (Thomas') and that is what (Morin) does when people steal from him," the affidavit said. An officer identified in the affidavit as B. Williams said he was sent to the scene Sunday evening to respond to a "found body call" and saw the body "was covered in debris and was missing its head and one arm." After obtaining a search warrant, he and other officers spotted a trash bag sticking out from under the house. As another officer was pulling the bag from underneath the house, "a finger poked through the bag from the inside," Williams said. The officer opened the bag, and police saw the head and arm and some bloody clothing, he said. Another officer found the chain saw, also under the house. Court records show Morin with an extensive criminal record since at least 1998 with charges that included auto theft, aggravated assault, marijuana possession and felony weapon possession.