Barnaby Jack, a celebrated computer hacker who could force a bank ATM to spit out cash and sparked safety improvements in medical devices, has died, The San Francisco Medical Examiner's Office said.

Jack died at his home in San Francisco Thursday. The cause of death is still under investigation, said San Francisco Deputy Coroner Kris Barbrich.

The thirtysomething techie was scheduled to speak about hacking pacemakers and other wireless implantable medical devices on Aug. 1 at the Black Hat conference, a well-known gathering of security experts, in Las Vegas. The headline of his talk was, "Implantable Medical Devices: Hacking Humans," according to a synopsis on the Black Hat conference website.

Jack planned to reveal software that uses a common transmitter to scan for and "interrogate" individual medical implants, the website said.

The topic is reminiscent of the second season of the TV drama "Homeland," when terrorists kill the vice president by hacking into his heart device. Jack planned to discuss ways manufacturers could improve the security of the devices.

The hacking community expressed shock as the news of his death spread via Twitter early on Friday.

"Wow ... Speechless," tweeted mobile phone hacker Tyler Shields.

Jack's most recent employer, the cyber security consulting firm IOActive Inc, said on its Twitter account: "Lost but never forgotten our beloved pirate, Barnaby Jack has passed."

Jennifer Steffens, the CEO of IOActive, Inc., called Jack one of the most accomplished security researchers. He dedicated his career to exploiting weaknesses in onboard computers in cars, automated teller machines and other so-called "embedded devices" so that they can be better protected.

"A truly visionary man in many ways, Barnaby's recent critical research into the safety of medical devices such as pacemakers leaves behind a legacy that will never be forgotten," Steffens said in a statement.

"IOActive will be working with the industry as a whole to ensure the advancements Barnaby started in this field will continue saving lives for years to come," she added.