Was this the owner saving the horse? It almost looks like passers by, which I hope not. If I had horses and knew flooding was coming I'd be doing absolutely everything to get my horses to higher ground, I certainly wouldnt let my horse stand there up to his ears almost in water when there was grass so nearby!
It certainly did look like passers by didn't it. The brave chap who got to the horse first looked a bit confused as to what the hell to do with it once he got there but full marks for his bravery and compassion. Then again the horse looked totally relaxed about him being there so maybe it did know him?
I am with you, if it were my horse there is nothing on earth that would keep me from trying to get him to higher ground. Hopefully it's not the case that the owners had been caught out by the water themselves...
A lot of people have been trapped on the wrong side of town and been unable to return to their homes. So maybe the owner is frantic somewhere and unable to do anything.