Clover, SC – A South Carolina woman fatally poisoned her husband using over-the-counter eye drops meant to reduce redness in the eyes.

York County Sheriff’s Office detectives arrested 52-year-old Lana Clayton for the murder of her husband, 64-year-old Stephen Clayton, on Aug. 31, according to a press release from the York County Sheriff’s Office.

The warrant served by detectives said that Lana had admitted to poisoning the water her husband drank from July 19 to July 21 with the chemical tetrahydrozoline, the Charlotte Observer reported.

Initially, police believed Stephen had died on July 21 from a fall down the stairs after his body was found in the foyer of the couple’s waterfront home on the shores of Lake Wylie.

Lana told investigators that Stephen had been suffering from vertigo for several days before he fell.

However, the toxicology report from the man’s death showed he had been poisoned with a chemical found in many over-the-counter nasal sprays and eye drops, according to the Charlotte Observer.

Lana was arrested 10 days after her husband’s death, much to the surprise of neighbors and friends who had known them as a happy couple.

“I’m just stunned,” Ken Sanford told the Charlotte Observer of his friends.

He described Lana Clayton as “a sweet lady” and said “Stephen was very proud of her accomplishments.”

Sanford said Stephen had “lovingly restored” the $822,000 home that was a copy of George Washington’s Mount Vernon estate. He also owned the property next door, valued at $385,000, the Charlotte Observer reported.

Lana had already been appointed personal representative for her husband’s estate by the York County Probate Court at the time that she was charged with murder and unlawful malicious tampering of food.

The sheriff’s department’s statement said that after she was arrested, Lana “admitted to investigators she administered the substance to Stephen Clayton without his knowledge.”

“We don’t have a clear cut reason why she committed the crime that she did, or what kind of motive she had,” York County Sheriff’s Office Spokesman Trent Faris told ABC News. “She revealed that she used the liquid which is known normally [as] eye drops, and put it in his food, and she did that without his knowledge.”

In light of Lana’s confession, authorities are going back to review an incident that occurred in the couple’s home in 2016, when Lana claimed she had shot Stephen with a crossbow “accidentally,” according to The Washington Post.

“We are making a comprehensive review of all events in the relationship between the defendant and the victim,” 16th Circuit Solicitor Kevin Brackett told the Charlotte Observer. “We will be taking a look at the relationship and the 2016 incident.”

In that instance, Lana went to the York County Sheriff’s Office and told deputies she had accidentally shot Stephen while trying to load the crossbow.

The police report said Lana told detectives that the arrow struck Stephen in the back of the head and “he woke up yelling and bleeding from the wound.”

Deputies went to the home and talked to Stephen, who told investigators that “he was fine and the shooting was accidental.”

He said that his wife had problems sleeping and sleepwalked, according to the police report.

Stephen told investigators at the time that he didn’t think his wife had shot him intentionally, “and he did not believe his wife was trying to kill him” when she shot him in the head as he slept, the Charlotte Observer reported.

During the investigation, Lana told detectives that her husband was mentally abusive and that he had “mood swings,” but that he had never hit her, the Charlotte Observer reported.

Detectives ruled the crossbow shooting an “accident” in May of 2017 and said in their report that “no intent to commit a crime was found.”