He was 86 (or thereabouts) in this clip. He died in 1964 at age 90.
Hoover was an "accidental spy." During the late 1890s and through to the beginning of WW1, Hoover was a mining engineer in various places including Australia, China and Russia. Fast forward to 1949... and the Soviets detonate their first nuclear device. The US is in a panic, the Cold War ignited. The CIA and military needed information on Russia but had little. Just by chance, the CIA learned of a vast collection of notes and maps held by Stanford University, which included information on Kyshtym, an area in Russia that the CIA believed was the source of their plutonium. As it happened, Hoover was a mining engineer in that area decades before, and mapped the region himself. He didn't throw anything away, and later donated all his notes to Stanford, his alma mater. The CIA had what they needed, and Hoover's information was used later when Gary Powers flew his ill-fated U2 surveillance flight into Russia in 1960. It's funny how history works, isn't it?