32-year-old Kasey Simmons waits tables at an Applebee's near Dallas and he was at a grocery store recently when he saw an older woman who looked upset.

The woman had apparently forgot her money, and she was only buying $17 worth of stuff. So Kasey paid for it, and didn't expect her to pay him back or anything.

But he was at work the next day when a family came in and sat down at one of his tables. All they ordered was a 37-cent glass of flavored water, which was literally the cheapest thing on the menu. Then they left.

Kasey probably thought they were just weird. But when he looked at their check, he realized it was the woman's family and they left him a tip for $500.

Kasey Simmons

Somehow her daughter figured out where Kasey worked. She left a note on her napkin that said her mom couldn't stop smiling after Kasey helped her out.

It turned out she was upset that day at the grocery store because it was the three-year anniversary of her husband's death. Kasey's random act of kindness made her whole day better. Her daughter just wanted to return the favor.

Read more at WFAA.