Former Secretary of Defense Ashton Carter has died at the age of 68 after suffering a “sudden cardiac event,” his family said in a statement Tuesday.

“It is with deep and profound sadness that the family of former Secretary of Defense Ashton B. Carter shares that Secretary Carter passed away Monday evening in Boston,” the family wrote.

Carter, known as “Ash,” served under former President Barack Obama as the nation’s 25th defense secretary from 2015 to 2017, during which he launched the fight against the ISIS terror group and opened combat roles in the military to all women.

President Biden, who was vice president during Carter’s time as defense secretary, said he “relied on Ash’s fierce intellect and wise counsel to ensure our military’s readiness, technological edge, and obligation” to the troops during Carter’s time in office.

“Ash was a leader on all the major national security issues of our times – from nuclear deterrence to proliferation prevention to missile defense to emerging technology challenges to the fight against Al Qaida [sic] and ISIS,” Biden said in a statement. “He opened every field of military service to women and protected the rights of transgender service members.”

Carter was on the forefront of acquiring and developing new technologies for the Defense Department, in 2015 standing up the Pentagon’s Defense Innovation Unit, a small office that acts as the point-of-contact between the commercial tech industry and the military.

“He was relentless in his pursuit of technology solutions for our warfighters, rapidly accelerating delivery of mine resistant vehicles to our troops to protect them from improvised explosive devices in Iraq and Afghanistan,” Biden said. “His work saved countless lives and limbs.”

Prior to his death, Carter served as director of the Harvard Kennedy School’s Belfer Center for Science and International Affairs, which conducts research, teaches students and trains professionals in “international security and diplomacy, environmental and resource issues, and science and technology policy.”

“For over 35 years inside government under presidents of both political parties as well as in the private sector, Carter leveraged his extraordinary experience in national security, technology, and innovation to defend the United States and make a better world,” the center said of Carter. “He was awarded the Defense Distinguished Service Medal, the Department’s highest civilian honor, on five separate occasions.”

Carter is survived by his wife Stephanie and two grown children, Ava and Will.

“He was a beloved husband, father, mentor, and friend. His sudden loss will be felt by all who knew him,” his family said. ““He believed that his most profound legacy would be the thousands of students he taught with the hope that they would make the world a better and safer place.”