The $1.5 billion Mega Millions jackpot winner came across her history-making lottery prize when she decided to go on a scenic drive during down-time on a trip to Greenville, South Carolina, her attorney said.

That's when she drove past a KC Mart, and when its signs about the jackpot caught her eye, she stopped in to buy a ticket, Jason Kurland, the attorney, said in a Thursday statement.

A customer fills out a play slip before purchasing Mega Millions lottery tickets at a retailer in Arlington, Va., Oct. 22, 2018. No winning tickets were sold for 19 October's Mega Millions drawing, a 44-state lottery,  and the jackpot now grows to 1.6 billion US dollars for the next drawing on 23 October 2018.(Erik S. Lesser/EPA/Rex/Shutterstock) A customer fills out a play slip before purchasing Mega Millions lottery tickets at a retailer in Arlington, Va., Oct. 22, 2018. No winning tickets were sold for 19 October's Mega Millions drawing, a 44-state lottery, and the jackpot now grows to 1.6 billion US dollars for the next drawing on 23 October 2018.

"After checking her ticket the morning after the drawing, she was in complete shock and disbelief," Kurland said. "She stared motionless at the ticket for what felt like hours, then came the jumping and screams of joy."

Words can't describe the feeling of such incredible luck.

The sole winner of the $1.5 billion Mega Millions jackpot from October 2018 came forward to claim her prize last week.

The winner, a South Carolina woman who chose to remain anonymous, selected the cash option of a one-time payment of $877,784,124. The payout is the largest to a single winner in U.S. history.

"Words can't describe the feeling of such incredible luck," the winner said in a statement released by her attorney Thursday. "I do realize that such good fortune carries a tremendous social responsibility, and it gives me a unique opportunity to assist, support and contribute to charities and causes that are close to my heart.”

Kurland said the winner is donating money to the Ronald McDonald House of Charities of Columbia, South Carolina, the Red Cross Alabama Region's tornado relief fund, the city of Simpsonville, South Carolina, Art Center, the One SC Fund for Hurricane Florence relief, and In The Middle, a Columbia, South Carolina, charity for women undergoing breast cancer treatment.

ABC News' Jenn Leong, Janice McDonald and Bill Hutchinson contributed to this report.