There's a number of possibilities.
Was he using one hand, or two?
A guy who is REALLY fast with just one hand will cock it with the thumb during the draw, fire with the trigger, then keep holding the trigger back while "thumbing off" another shot. YES, you can do this with an SA revolver. It's a bit tough on the gun but not TOO bad...technically the second shot is being "hammer slipped" with the thumb. You can get off a whole string of hammer-fired shots while holding the trigger back.
"Fanning" means he did the same basic thing but on the second shot, swiped the hammer with his off-hand palm. Again, the trigger is pulled back on the first and all subsequent shots.
The most difficult variant is the "five fingered fan". Strong-hand thumb cocks during the draw, strong-hand trigger finger fires and holds, and then each finger on the off-hand fires another shot in turn...imagine curling all your fingers in sequence. All five rounds can fire in less than a second...this is with either very light loads or more likely, blanks. Rate of fire borders full-auto territory...sounds like a single "riiiip".
"Fanning" beats the hell out of the gun. Bob Munden is both a gunsmith and artist with this stuff, entering various trick-shooting competitions and beefing Rugers up to where they'll cope with these stresses, at least for a while. The safety gets ditched, among other mods...