He was 90 years old.

Peter Buck, the co-founder of the American Subway fast food chain, has died at the age of 90. The company announced this on Twitter on Saturday.

“Our co-founder Peter Buck has died. He was 90 years old. Kind-hearted physicist and philanthropist Dr. Buck has made a lasting impact, leaving behind a spirit of hard work and dedication in each of the network’s nearly 40,000 locations. His legacy lives on in the Subway brand, which he worked hard to create,” the message reads. The cause of death is not specified.

In 1965, Peter Bank lent $1,000 to the future founder of the Subway network, Fred DeLuca, who was 17 years old at the time. With this money, De Luca opened the first sandwich shop to earn money for university tuition. In 1968, the chain received its modern name Subway, and 10 years later it had 100 fast food outlets. The Subway network already has more than 40,000 restaurants in 112 countries around the world.