The video is here
Out of curiousity, how much turn-out does Reggie get? Horses kept in stalls for many hours of the day will get stressed out, especially ones with "aggressive" personalities like my boy Freddy, and they develop vices or behaviour problems that help channel their energy.
This "attack for no reason" could be caused by the lack of turn-out (and also lack of variation in work, horses get bored and depressed from doing the same things all the time.) that he gets. Healthy turn-out for most horses is around six to eight hours.