I suggest you ALL have a look at the replay. There were at least two emergency vehicles there and the guy making sure they stayed clear was wearing a yellow jacket suggesting he was either a medic or vet. I am surprised they didn’t get the screens up though.
As for keeping a horse down I’ve always heard that sitting on their necks does the job. If they can’t lift their heads they can’t get the leverage to get up.
RIP Marden Court.