The school guidance counselor found dead behind her home near Wiggins was decapitated, Stone County Coroner Wayne Flurry said.
The body of 51-year-old Sherry Johnson had been in the backyard of her home on Johnson Road for two or three days, Flurry said.
Johnson's son, Terrelle Johnson, was arrested on a first-degree murder charge, sheriff's Capt. Ray Boggs said Friday.
The woman's torso was lying near a fence and a head was found 15 feet away, he said.
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"Crime lab tests confirm the torso did belong to Sherry Johnson, but we have not been able to get ahold of dental records that would positively show the head is hers," Flurry said.
"We've got to make sure the head matches the body."
DNA tests and other tests will be done. Those results could be available Monday, Flurry said.
"I've heard all kinds of crazy rumors, such as she was dismembered," he said.
"The full exam was done in Jackson and I have not been able to speak to the doctor yet, but I did not see any other lacerations or puncture wounds to her body when I saw her."
Johnson had worked at Hattiesburg High School since 2014. The school family admired her "can-do" attitude and willingness to find solutions for problems, Principal Eric K. Boney said.
The remains were found early Wednesday evening when deputies responded to a call asking for someone to check on Johnson.
Terrelle Johnson is being held with no bond at the Stone County Jail on an order by Justice Court Judge Justin Miles, said Boggs, the sheriff's chief investigator.
"Mr. Johnson has been interviewed, but I want to wait until the head has been identified before I release a full statement," Boggs said.
A date for a preliminary hearing has not been set.