COLUMBIA -- A man suspected of killing his mother-in-law was arrested late Thursday as police tried to unravel the multifaceted case that also includes a poisoning allegation and a fire at the family's home.

Kenneth Ray Moore had been on the run since Tuesday, when police say he shot 58-year-old Fay Fagan to death in the parking lot of an eye care center.

Moore's wife, 36-year-old Denise Fagan, was sitting in a truck with her parents when Moore walked up and demanded that his wife leave with him. When she refused, Moore told his mother-in-law that he was going to kill her, then shot her twice, according to authorities. He also threatened to shoot his wife, who then left with her husband and was released unharmed an hour later, police said.

Denise Fagan's father reported the shooting, police said.

Moore was arrested Thursday night after a customer recognized him at a Walmart in Greer, about 18 miles from the shooting, police said.

Questioned extensively by investigators, Moore has been cooperative and confessed to the shooting, according to police.

"He really did not offer up a reason as to why he shot his mother-in-law," Spartanburg Public Safety Capt. Randy Hardy said Friday. "The only thing he would say to us is that he did something stupid. He said he just snapped."

Bond has not been set for Moore, 37, who is charged with murder, possession of a weapon during a violent crime and kidnapping. He was being held Friday at the Spartanburg County jail, and his next court appearance is set for June 24.

A message left with an attorney, who police said was representing Moore, was not returned.

Fay Fagan's death is only one component of the complex case facing investigators. About two weeks before the shooting, Moore was admitted to Spartanburg Regional Hospital, complaining of hallucinations and cognition problems. He said the issues had started in October, when he noticed a bitter taste showing up in his food and drinks.

While he was hospitalized, Moore's wife brought him food and drinks from home, including "Holy water," "Holy Sprite" and lumpy gelatin, according to a police report. His conditions worsened as he ate and drank them, and hospital staff began to think Moore was being poisoned. Doctors ordered that Moore eat only hospital food, and the hallucinations stopped, police said.

On March 24, Moore filed a police report, accusing his wife of poisoning him. In his hospital room, police found a bag of crushed pills that included medication for depression and heart problems -- medicines Moore was not taking.

Questioned about the pills, Denise Fagan told police they had been prescribed to her, saying she had crushed the pills to make them easier to take, Hardy said Friday. And authorities found traces of the drugs in a pudding cup taken from Moore's hospital room, Hardy said.

"If someone's not prescribed those drugs, they could make those hallucinations happen," Hardy said. "The problem with that is, we know that kind of medication was put into those items while he was in the hospital. The problem is, who put them in there?"

Fagan denied ever lacing her husband's food and has not been charged in the case, which Hardy said is ongoing.

Before the shooting, she had begun the process of having a restraining order taken out against her husband, but Fagan never finished the paperwork, Hardy said.

Also, on April 4, the couple's home caught on fire while Moore was at church, Hardy said. Denise Fagan has been questioned, and Hardy said she is suspected of arson. However, no charges have been filed.

A working phone number for Denise Fagan could not be found.