A man who fatally stabbed a convenience store clerk during a robbery 23 years ago apologized repeatedly to her relatives and to his mother before he was executed Tuesday.

"I know I hurt you very bad," Michael Lynn Riley said to his victim's relatives, including her two daughters and husband. "I want you to know I'm sorry."

Brandy Oaks said she accepted Riley's apology and was pleased to hear it. She was 4 when her mother, Wynona Harris, was killed.

"This is a difficult day and there are no winners on either side," Oaks said. "Her spirit will live on in our hearts and in our lives."

Riley, 51, also apologized to his mother, who was not present, for being "not the big son that you wanted me to be."

Eight minutes after the lethal drugs began to flow, he was pronounced dead at 6:18 p.m. Riley was the 15th murderer executed this year in the nation's most active death penalty state.

He was condemned for killing the 23-year-old Harris at a convenience store in Quitman, about 75 miles east of Dallas. Riley was a frequent customer, and Harris told him to help himself to the ice cream he wanted that Saturday morning while she counted some money.

Instead, he stabbed and slashed her repeatedly with a 10-inch butcher knife, then fled with about $1,000. Bloody footprints led detectives toward Riley's home a few blocks away.

He said gambling losses in a dice game prompted the killing.

"Dice took my life," Riley told The Associated Press in a recent interview from prison. "It's the worst drug habit you can have. I wanted to try to live the big life. I was trying to live the life of a high roller."

Riley had a record for burglary and other crimes before the slaying, and he was among the longest-serving of Texas' 334 condemned prisoners. His first conviction in the case was overturned because a potential juror was dismissed improperly.

At his retrial in 1995, he pleaded guilty and defense lawyers argued for life in prison. Prosecutors sought death and jurors agreed with them.

"I have no hate," he said. "I was very sorry for what I did."

At least six other Texas death row inmates have execution dates in the coming months.