Good guess Nitro.
Yup, the big 600 said bang- click instead of bang- bang. Misfire-Left Barrel!
The client only had one round left for his 470 and they did the usual walk up to the wounded bull which of course charged and was nicely brained by the client I think, with Sullivans bullet going a tad high and maybe creasing the top of the boss.(due to the bull dropping it's head from the clients brain shot)
The bull fell right at Sullivans feet and when he went to give it the second barrel there was only this little "click".
Nothing was said about it on the video so I don't know if the problem was with the cartridge or with the gun.