Apple‘s health boss, Anil Sethi, has left the company to start venture focusing on helping very sick patients after his sister died from cancer.

Sethi’s medical record start-up Gliimpse was acquired by Apple in August 2016, with Sethi named director of the health team. Sethi also worked at Apple as an engineer in the late 1980s but doesn’t credit that as a factor in the acquisition. Instead, he suspects, it was his team’s expertise at aggregating medical information, while adhering to federal privacy requirements.

“At one point, Cupertino looked at 50 companies or so but they picked our team,” he said. “I can’t speak for them but one of the things we did is showed them a demo of what the technology could do without a slick deck.”

Apple has been looking at ways to turn the iPhone into the central vault for people’s medical information. That’s Sethi’s expertise, which he views as a key way to get around health care’s “interoperability problem.”

Interoperability, meaning the ability to share medical information securely between hospitals and clinics, is still a challenge in health care. It particularly affects those with serious health conditions with records scattered among dozens of doctors.

Sethi had been on leave from Apple for several months to care full-time for his sister, Tania. One of Sethi’s goals with Gliimpse was to help her aggregate her medical information, including labs and charts.

She died of cancer on Sept. 11.

He since decided not to rejoin the Apple health team and instead is starting a new company, dubbed Ciitizen, which is focused on making it easier for people like Tania to get their information — whether it’s about genomes, labs, ethical wills or advanced directives — and share it with researchers on request. He describes it as “health data as a palliative.”

Sethi made his sister a promise in her final days to dedicate his life to improving cancer care for patients. He said Apple COO Jeff Williams personally gave him the time off he needed to care for her.

He describes his start-up as “depth rather than breadth.” He said that Apple has the opportunity to help more than 1 billion people by adding more health capabilities to iOS devices but in ways that are “not as deep.”

But Sethi stressed that Apple’s executives are personally excited about the opportunity in health. Eventually, he hopes to meet his former colleagues “in the middle,” as Apple continues to work in health and wellness but starts to branch out into more medical applications like using Apple Watch to detect the heart rhythm disorder atrial fibrillation with a goal of saving lives.

Sethi is self-funding the venture but is looking to raise a round of financing in the spring. In the meantime, he’s building a team of senior engineers.

Sethi will announce the new venture at a San Francisco conference for designers and technologists working on end-of-life experiences, called EndWell, on Thursday.