The Bull was already charging...within metres..I'd hope by then I too would have the bolt locked & the gun coming up. You're talking about only 1 or 2 seconds to react here. In falling though, reflex or instinct should have released the figure from the trigger. I believe that comes with experience & familiarity with firearms.
Such events give us all the horrors... as they should.. but as ozhunter says we are all far from perfect.
Speedy recovery to Stuart Taylor.