Tristan O'Tierney

Tristan O’Tierney, a co-founder of San Francisco payments company Square, died Feb. 23 in Ocala, Fla., of causes related to addiction, his family said. He was 35. Born on a naval base in Adak, Alaska, O’Tierney grew up in different states before settling in New York. He attended Rochester Institute of Technology from 2001 to 2008 and graduated with a degree in computer science. He first came to the Bay Area in 2005, when he worked as a software engineer at Yahoo. He went on to hold positions at Apple, VMware, and Tapulous. Jack Dorsey and Jim McKelvey hired O’Tierney to develop Square’s original mobile payment app in early 2009, and O’Tierney is generally credited as a co-founder. He left the company in 2013. He is survived by his three-year-old daughter, Rumi Ari; his girlfriend, Anjela Ramos; parents Mark and Pamela Tierney; and half sister Terri Lynn Cloud.