According to the summary:
On July 19, 1957, five men stood at Ground Zero of an atomic test that was being conducted at the Nevada Test Site. This was the test of a 2KT (kiloton) MB-1 nuclear air-to-air rocket launched from an F-89 Scorpion interceptor. The nuclear missile detonated 10,000 ft above their heads.
A reel-to-reel tape recorder was present to record their experience. You can see and hear the men react to the shock wave moments after the detonation.
The placard reading "Ground Zero; Population Five" was made by Colonel Arthur B. "Barney" Oldfield, the Public Information Officer for the Continental Air Defense Command in Colorado Spring who arranged for the volunteers to participate.
The five volunteers were:
Colonel Sidney Bruce
Lt. Colonel Frank P. Ball (technical advisor to the Steve Canyon tv show)
Major Norman "Bodie" Bodinger
Major John Hughes
and George Yoshitake, the cameraman (who wasn't a volunteer)
So was George Yoshitake strong-armed into filming this or did he set the camera up and then flee to the relative safety of a lead-lined viewing area? Are these volunteers still alive? Are they riddled with cancer? Answer me, YouTube summary!
Oh wait, it looks like NPR did some digging and found out the fate of many of the volunteers did end in cancer. However, cameraman George Yoshitake is alive and well (or was as of 2010) leading me to believe he set up the camera and then ran away. Probably making "Whoop whoop whoop" noises and scuttling like a human Dr. Zoidberg.