Igor M. Ponomarev, a Philadelphia lawyer on the rise as a financial crimes investigator at Wells Fargo, was 28 when his life was profoundly changed by bad and good fortune.

In October 2018, he was diagnosed with advanced, incurable stomach cancer. Days later, at Pennsylvania Hospital, he met the woman who would become his fiancée, Jennifer Cortese, an oncology nurse.

“I fell in love with him right away,” Cortese said. “It was mutual, but we just exchanged emails and waited until he was no longer in care to communicate outside the hospital. Once we started dating, he said it was his goal in life to make me as happy as possible every day. And he did.”

Mr. Ponomarev died Monday, Jan. 6, at age 29 after 15 months filled with chemotherapy, surgery, stoicism, and love.

“In March, he was feeling fine,” his mother, Natella Ioffe, said. “He moved back to his apartment in Northern Liberties, he returned to work, and they started dating. She was so dedicated to him. He told me: ‘I know I’m sick, but she’s the one. I’m going to ask her to marry me.’ ”

Mr. Ponomarev was born in Moscow in 1990. At age 8, he and his mother emigrated, eventually settling in Fairfield, N.J. “It wasn’t a good time in Russia in the 1990s,” Ioffe recalled. “I thought Igor would have a much better life in the U.S.”

Mr. Ponomarev graduated in 2012 from the College of New Jersey with a degree in international business — and awards from Sigma Alpha Epsilon fraternity for leading charitable work. He went on to Villanova University’s law school, where he earned a law degree and a master’s degree in tax law, served as an editor of the law journal, and won a public-service award for working at Villanova’s low-income tax clinic.

“Igor was impeccably polite,” Cortese said. “He was also outstandingly witty and had the ability to make a clever joke at breakneck speed. He had a gift for making absolutely everything fun.”

After being hired by Wells Fargo in late 2017, Mr. Ponomarev was trained in anti-money laundering investigations. “He really loved that,” his mother said. “And everybody there loved him.”

About two months ago, with his cancer progressing, Mr. Ponomarev entered the Hospital of the University of Pennsylvania.

“He was really hoping he’d get better and buy a ring,” his mother said. “But he couldn’t. So he proposed to her in the hospital.”

Cortese didn’t hesitate to say yes. She cherishes the family heirloom ring he gave her.

Besides his mother, he is survived by his stepfather, Michael Ioffe; his father, Michail, and stepmother, Elena Ponomarev; a grandmother; and an uncle. Per his wishes, there will be no services, but donations in his honor can be made to Debbie’s Dream Foundation: Curing Stomach Cancer.