He admitted that he was struggling with depression when he walked into Albert's Pizza in Ronkonkoma, New York, CBS New York reported.
He received a free pizza as part of a “pay it forward with pizza” campaign.
Kind customers had stepped forward to pay for pizzas for police officers, single mothers and people like Kust who are struggling.
When Kust opened up the pizza box from an anonymous donor, he found, written in colorful letters, a message that read “Stay strong.”
It’s the same message that he heard his wife say every day before she died.
"The last month of my wife's life, she kept telling me, 'You have to be strong, you have to be strong,'" Kust told CBS New York.
Kust said the pizza box’s message convinced him that his wife was still with him.
He went back to the store later to thank the owners and to give them a handwritten letter explaining how much the simple act of kindness meant.
“You don’t know me, but on March 25th, you turned my life around,” the letter read.
Rich Baer, co-owner of Albert’s, said he has read the letter dozens of times, and it always brings him to tears.
"When you do something nice, it works. You see somebody benefit," Baer told CBS New York.
Kust also stepped up to anonymously buy a pie for someone else.
It’s unclear how the pizza restaurant knew that Kust was going through a tough time, but the action affected him in an important way.
“I’d like to somehow thank the people who bought it for me and let them know they saved my life,” he told CBS.
The pay it forward pizza movement is growing rapidly, with dozens of customers buying pizzas for others. Like Kust, most are donating anonymously.