Washington, Dec 29 (IANS): An American social worker who died of cancer has left behind $11 million for children's charities in the US city of Seattle.

No one who knew Alan Naiman could have guessed he had amassed a fortune. The frugal social worker bought his clothes at Costco, cut coupons and liked to take thrifty road trips for his holidays, the BBC reported on Friday.

But when he left $11 million to the charities, friends say they were not surprised by his generosity.

Naiman died in January 2018 of cancer at age 63 in Seattle, Washington.

"I think everyone was shocked, I mean really shocked that he had so much money to give away," says his friend Mary Monahan, who worked with Naiman at Washington state children's services.

Soon after being diagnosed with cancer, he told her that he would donate everything he had to charity upon his death."People will be surprised at the amount," she recalls him saying."Yeah, people were -- I'm sure -- very surprised," she told the BBC.

Naiman left a lucrative banking career to work with children 30 years ago.

Monahan believes his experiences working with children in social services, many of whom had disabilities, inspired him to put others first."I guess he thought he had what he needed, and a lot of other people didn't have what they needed," she says.

"The kids that came into care got into Alan's heart."

Naiman inherited some of his wealth from his parents, but he also saved and invested most of his earnings throughout his life.