Tristan O&Tierney, a co-founder of the payments company Square, has passed away at age 35.

According to the San Francisco Chronicle, O&Tierney died last weekend in Florida of addiction-related causes after a hospital was unable to revive him. In the Chron piece, it reports that Square co-founders Jack Dorsey and Jim McKelvey hired O&Tierney to develop Square original mobile payment app in early 2009, and that O&Tierney is generally credited as a co-founder. He left the company in 2013, eight years after coming to the Bay Area, where he also worked as a software engineer at Yahoo for nearly two years and worked briefly at Apple, VMware and Tapulous. In recent years, O&Tierney had been working as a freelance photographer in Los Angeles, according to his LinkedIn profile.

(You can check out some of his work here.) He was also the director of Mobile at a short-lived San Francisco-based company, Voteraide, that aimed to empower voters by enabling them to interact with candidates and elected officials as verified voters. O&Tierney was reportedly in Florida as part of a months-long rehabilitation program. Dom Sagolla, a former colleague and roommate of O&Tierney, tells the Chron it was he who introduced O&Tierney to Dorsey 11 years ago.

He says O&Tierney had helped to develop the official iPhone app for Barack Obama 2008 presidential campaign and that O&Tierney and Dorsey met at an iPhone-app development event that he organized.

&I will really miss him and want his memory and legacy to last,& said Sagolla. O&Tierney clearly had varied interests.

Though he studied computer science at the Rochester Institute of Technology, he also later obtained a Master of Fine Arts degree from the San Francisco Art Institute.

On Instagram, his descriptor reads: &Square co-founder turned traveling photographer.

Searching for the meaning of life and got lost along the way.& Pictured above: a landscape photo of Death Valley by O&Tierney.