A South Dakota inmate has been executed for the 1990 rape and murder of a 9-year-old girl who disappeared after leaving her home to buy sugar for lemonade.

Sixty-year-old Donald Moeller received a lethal injection Tuesday night at the state penitentiary in Sioux Falls, marking the state's second execution this month.

Moeller kidnapped Becky O'Connell from a Sioux Falls convenience store in May 1990, then raped and stabbed her. Her naked body was found the next day near the Big Sioux River.

Becky's mother, Tina Curl, has been steadfast in her wish to watch Moeller die. She raised money so she could travel from her New York home to watch the execution.

Curl says Moeller watched her daughter take her last breath, and she wanted to watch him take his.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

Becky O'Connell left her South Dakota home on the simplest of errands: to go to the store for sugar so she could make lemonade.

When the 9-year-old didn't return, panic gripped Sioux Falls, prompting parents to round up their children and keep them indoors. But within hours, the mystery was solved _ with a gruesome outcome.

Becky had been kidnapped, raped and stabbed to death, left to die on an earthen berm near the Big Sioux River that rainy night in May 1990.

Becky's killer, 60-year-old Donald Moeller, is set to die by lethal injection Tuesday night at the South Dakota State Penitentiary.

And her mother, Tina Curl, has been steadfast in her wish to watch him die, raising funds to cover the expenses to make the 1,400-mile trip from her home in New York state to return to Sioux Falls for the execution.

"He watched my daughter take her last breath. I want to watch him take his last breath," Curl told The Associated Press in August. "I'm doing this for her and for me."

The death 22 years ago changed Sioux Falls, a city where South Dakota, Minnesota and Iowa meet. Murders are rare here, numbering fewer than 10 a year, with most of those committed by people who know their victims.

"She moved here because it was the safest state to live in for her daughter," said Audrey Reyelts, 65, who worked with Curl at a Holiday Inn at the time of the murder. "It wasn't too long after they moved that the little girl disappeared. I couldn't believe it because she was so protective. That little girl was all she talked about."

Reyelts had already been strict with her own children, but got stricter after Becky's death, said her daughter, Tonya Reyelts-Doese.

"Everything changed," said Reyelts-Doese, who said the crime made her "overly cautious" when raising her own children years later. "I think that's when (schools and police) really emphasized security for the kids, going through schools to give them a heads-up on how to handle a situation like that."

Reyelts-Does, 37, plans to await the execution outside the prison Tuesday night in a show of support for her mother's long-ago friend.

The long-term effects on Curl have been devastating. She moved to Lake Luzerne, N.Y., shortly after Becky's death, and has battled alcoholism and suffered a heart attack.

When speaking of her daughter's death, she doesn't temper her anger.

"It won't bring me closure," she has said of Moeller's execution. "It will bring me relief that he's dead and he'll never get to do this to anybody else's child."

South Dakota Attorney General Marty Jackley said he hopes the end of the legal saga keeps the focus on the girl, who this year would have been 31.

"Sometimes I think the victims get lost in ensuring that a defendant receives due process," he said Monday.

While prison officials anticipate protesters to gather outside the prison, Moeller himself has fought a flurry of motions filed on his behalf to halt his execution. In July, he finally acknowledged killing Becky, and said it was time he paid for his crime.

"I don't want to die," he said, assuring a federal judge that he didn't simply have a death wish after so many years on death row. "I want to pay for what I owe."

The execution will be South Dakota's second in as many weeks, an unusual surge in a state that has carried out just three death sentences since 1913.

The most recent was the Oct. 15 execution of Eric Robert for killing South Dakota prison guard Ronald "R.J." Johnson during a failed escape attempt.

Elijah Page died by lethal injection in 2007 for the murder of Chester Allan Poage, who was abducted and killed in a scheme to burglarize his mother's home. In 1947, George Sitts was electrocuted for killing two law enforcement officers. And in 1913, Joseph Rickman was hanged for the murder of a woman and her daughter.

They were among 17 inmates executed since 1877, the oldest of which came during the days of the Dakota Territory.

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Associated Press News Editor Amber Hunt contributed to this report.