BROGDEN, N.C. — Johnston County authorities say a woman accused of killing her 4-year-old adopted son used a piece of PVC pipe to discipline her children.

Lynn Marie Paddock, 45, was arrested Sunday night in connection with the death of the Sean Paddock, who was found unresponsive in his bed Sunday morning.

"This is one of the toughest things about being sheriff, dealing with children who have been abused," Johnston County Sheriff Steve Bizzell said. "This is one of the worst cases of child abuse that I have ever seen."

Family members told investigators that Sean was put to bed at about 10 p.m. Saturday, and that he was breathing when his mother checked on him at about 3:30 a.m. Sunday. But the next morning, at about 7 a.m., he would not wake up.

Sean was pronounced dead upon arrival at Johnston County Memorial Hospital.

Paddock was initially arrested Sunday night and charged with felony child abuse after severe bruising was found on at least two of her other children, ages 8 and 9, according to arrest warrants.

She was later charged with first-degree murder in connection with the boy's death. The charge, however, was reduced to second-degree murder Monday, and she is being held in the Johnston County Jail under a $1 million bond.

Paddock has seven children, six of whom are adopted, including Sean. It was just seven months ago that Paddock, and her husband Johnny Paddock, adopted the three children she is now accused of abusing.

The seventh child is a biological child of Paddock's husband, who has not been charged in the case. Investigators are not sure what, if anything, he knew about the abuse.

The Department of Social Services removed four of the remaining children from the Paddock home; two older teens, however, remained with their father.

Investigators said the investigation is ongoing. The child's body was taken to the Office of the State Medical Examiner in Chapel Hill for an autopsy.

"Over the next few days, the details are just going to be unreal," Bizzell said. "You are not going to believe it."

Neighbors who live near the Paddocks' remote farmhouse were troubled by Paddock's arrest.

"We were shocked," said Sheila Horton, who only met the Paddocks once since they moved from Raleigh two years ago. "Because we live out here, and everybody is real friendly."

The Paddocks run a carpet-cleaning business and have a 12-acre farm. Lynn Paddock taught the children at home. According to state records, she home-schooled the children since 1998, but not all of them were listed as being home-schooled. Authorities are also investigating this aspect of the case.