It reminds me of the Slotin Incident (http://www.damninteresting.com/bitten-by-the-nuclear-dragon/) where dr. Louis Slotin accidently slipped the screwdriver he used to separate two plutonium/uranium hemispheres:
"Immediately, all eight scientists in the room felt a wave of heat accompanied by a blue glow as the plutonium sphere vomited an invisible burst of gamma and neutron radiation into the room. As the lab's Geiger counter clicked hysterically, Louis used his bare hand to push the upper plutonium hemisphere off and onto the floor, which terminated the supercritical reaction moments after it began."
Big oopsie.
However gruesome the goal of these bombs, the rate of advancement in such a short timespan is nothing short of amazing. From the very first successful test (Trinity) to bombing Hiroshima: just 21 days. They were great days for science, but a shame to mankind that it had to come this far.