McDonald’s cashier Hunter Hostetler is on the lookout for the customer who started a 167-driver pay-it-forward chain at the Scottsburg, Indiana, McDonald’s where Hostetler has worked since October.

“I keep looking for her, hoping I see her and can tell her what happened,” Hostetler told ABC News. “I don’t know if she knows, but I hope to see her again so I can tell her.”

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Hostetler, 19, was working the drive-thru on Sunday night when, at around 8:30 p.m., the mystery woman drove to the window to pick up her approximately $6 food order.

When the woman, whom Hostetler described as being in her early 60s, saw there was a man with four kids in the car behind her, she told Hostetler she’d pay for his $36 food order too.

“She paid it in full and told me to tell the dad Happy Father’s Day,” Hostetler recalled.

When Hostetler told the man that his four Happy Meals and other food were paid for, he offered to pay for the next two cars behind him.

“It just snowballed from there up until we closed,” Hostetler said.

When Hostetler closed the drive-thru at midnight, the total number of cars who had joined the pay it forward chain was up to 167.

“It was very heartwarming,” Hostetler said. “The last customer who came through even asked if there was another car and I said, ‘Ma’am I’m sorry you’re our last customer for the night. We’re closing.’”

Abby Smith, 22, said she and her boyfriend made a last-minute decision to go to McDonald’s around 11:30 p.m. on Sunday and were shocked to find themselves as car No. 161 in the chain.

“I was just shocked because of the large number,” Smith said. “I didn’t even think about it I just said, ‘Go ahead, take what the previous person put down. Go ahead and take that from us too.’”

She added, "This made me feel like it was just a big family congregation. It was such a great feeling.”

Hostetler recalled that customers like Smith paid little attention to whether or not the meal they were paying for was three or four times the cost of what they ordered for themselves. For customers who could not afford to pay the difference, Hostetler and his colleague, Jessica Wells, donated money out of their own pockets to help.

“There’s so much negativity in the world,” Hostetler said. “Something like this just doesn’t happen every day.”

Frank Ward, the owner of the Scottsburg McDonald's, described the chain as an "act of kindness."

"McDonald's believes in supporting the local communities in which we operate," Ward said in a statement to ABC News. "I was proud to experience the Scottsburg community come together in this act of kindness under the Golden Arches."