Developer helped small businesses accept credit cards...

Tristan O'Tierney was the co-founder of Square, the mobile payment app that allows small businesspeople to accept credit cards via their smartphones or tablets. He began developing the app in 2009 and remained with Square until 2013. O'Tierney had also worked on former President Barack Obama's 2008 campaign app, and he had worked at tech companies including Yahoo! and Apple.

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Died: February 23, 2019 (Who else died on February 23?)

Details of death: Died in Ocala, Florida at the age of 35.

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Struggles with addiction: O'Tierney often spoke frankly online about his addiction. He had been in a rehabilitation program at the time of his death. His mother told the San Francisco Chronicle that his death occurred "in relation to his addiction."

He took pride in his work: “I helped start a company called Square to let regular folks accept credit cards just like the big boys.” —from O'Tierney's personal website

What people said about him: “Tristan was a person who is about as good-hearted as you could ask, dedicating himself to do something no one really gets selected to do, you put yourself forward. I just love that Tristan was there for Obama, he was there for Jack [Dorsey, founder of Square and Twitter]. His original sketches are framed and hand in Square's office. He's not just a programmer but a designer too, and that's a rare combination.” —Dom Sagolla, Twitter co-creator

“Saddened to hear of @tristan's passing over the weekend. I still remember building the first Square app together all of those years ago. He was always excited to build something new.” —Square founding designer Robert Anderson

Full obituary: San Francisco Chronicle

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