I had assumed it was an accident, not intentional. It is, after all, spring, and even usually well behaved horses can get a bit uppity at this time of year, especially if the care giver is not perceived to be the alpha of the “herd”. The problem now is what to do until the OP can be home long enough to restore the horse’s respect for humans in general. If he is by nature a horse who will graze himself sick on spring grass, then he either has to be in a dry paddock or his grass intake has to be limited some other way, such as a grazing muzzle. You may have to do some experimenting to find what will work, and find somebody other than your mother to get the grazing muzzle on him. The alpha horse in a herd dominates as much mentally as he/she does physically – – most of the time he/she only has to glare at a would-be usurper, & the would-be usurper backs off, but if that does not happen, the alpha horse will defend his position physically. This is the language horses understand. The best temporary solution will be one that keeps everybody intact & uninjured and not colic-ing on spring grass until the horse’s normal alpha human can get home & sort out his correct place in the “herd”. Are we talking weeks or months here? And is there someone else who can care for the horse until that happens, and who is a sufficiently alpha personality to be safe around the horse?